[Updated: February 11, 2014]

Surface Contaminants, Skin Exposure, Biological Monitoring and Other Analyses

Table of Contents:

1. Introduction
2. Basics of Skin Exposure
3. Wipe Sampling, Field Portable X-Ray Fluorescence Sampling, Dermal Sampling and Biological Monitoring
4. Sampling Methodology
5. Other Analyses
6. Enforcement Recommendations
7. Custom Services Provided by SLTC
8. References

 

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I. Introduction

The purpose of this chapter is to provide guidance to OSHA Compliance Safety and Health Officers (CSHOs) and to the industrial hygiene community on the potential for skin exposure to chemicals in the workplace and the available means of assessing the extent of skin exposure. This chapter provides guidance for the use and interpretation of surface wipe sampling for assessing potential contamination which may lead to biological uptake through inhalation, ingestion, or dermal exposure. This chapter discusses methods for assessing skin contamination, such as dermal dosimeters (e.g., sorbent pads) and dermal wipe sampling, and provides guidance for monitoring of biological uptake. Finally, this chapter provides guidance for certain specialized analyses unrelated to dermal exposure, such as soil analysis, materials failure analysis, explosibility determinations, and identification of unknowns.

Skin exposure to chemicals in the workplace is a significant problem in the United States. Both the number of cases and the rate of skin disorders exceed recordable respiratory conditions. In 2010, 34,400 recordable skin diseases or disorders were reported by the Bureau of Labor Statistics (BLS) at a rate of 3.4 illnesses per 10,000 full-time employees, compared to 19,300 respiratory conditions with a rate of 1.9 illnesses per 10,000 full-time employees (BLS, 2011).

In addition to causing skin diseases, many chemicals that are readily absorbed through the skin can cause other health effects and contribute to the dose absorbed by inhalation of the chemical from the air. Skin absorption can occur without being noticed by the worker. This is particularly true for non-volatile chemicals that are hazardous and which remain on work surfaces for long periods of time. The number of occupational illnesses caused by skin absorption of chemicals is not known. However, of the estimated 60,000 deaths and 860,000 occupational illnesses per year in the United States attributed to occupational exposures, even a relatively small percentage caused by skin absorption would represent a significant health risk (Boeniger, 2003).

Biological monitoring refers to testing which is conducted to determine whether uptake of a chemical into the body has occurred. Biological monitoring tests assess a sample of a worker's urine, blood, exhaled breath, or other biological media to evaluate the presence of a chemical or its metabolite, or a biochemical change characteristic of exposure to a particular chemical. Biological exposure guidelines such as the American Conference of Governmental Industrial Hygienists (ACGIH) Biological Exposure Indices (BEIs) are numerical values below which it is believed nearly all workers will not experience adverse health effects. The BEI values correspond to the biological uptake that would occur in workers exposed to airborne concentrations at the ACGIH Threshold Limit Value (TLV).  When biological monitoring indicates that workers have been exposed to a chemical, but the airborne concentrations are below any exposure limits, it suggests that exposures are occurring by another route, such as dermal absorption and/or ingestion.

Where other exposure routes are suspected, surface wipe sampling may be useful. Surface wipe sampling in areas where food and beverages are consumed and stored (including water bubblers, coolers, and drinking fountains) can be used to assess the potential for ingestion or dermal exposure. Such wipe sampling results can be used to support citations for violations of the Sanitation standard, 29 CFR 1910.141, or the applicable housekeeping provisions of the expanded health standards, such as Chromium (VI), 29 CFR 1910.1026. To assess the potential for skin absorption, surface wipe sampling in work areas may be used to show the potential for contact with contaminated surfaces. Such results could be used to support violations of the Personal Protective Equipment (PPE) standard, 29 CFR 1910.132(a), or applicable provisions of the expanded health standards, such as the Methylenedianiline standard, 29 CFR 1910.1050. For direct assessment of skin contamination, skin wipe sampling or dermal dosimetry may be used.

In addition, Section V of this chapter, Other Analyses, provides guidance for submitting samples to the Salt Lake Technical Center (SLTC) for specialized analyses including:

• Soil analysis in support of the Excavation standard (29 CFR 1926 - Subpart P - Excavations).
• Materials failure analysis.
• Explosibility determinations including:  
  • Combustible dust analysis
  • Flash points
  • Energetic reactivity of chemicals
  • Autoignition temperatures
• Biological sampling for organisms (or chemicals associated with their presence) such as:
  • Fungi
  • Bacteria (such as Legionella)
  • Endotoxin (component of the outer membrane of certain gram-negative bacteria)
• Mass spectrometry analysis for identification of unknown materials in:
  • Industrial processes
  • Indoor air samples
  • Contaminated water samples

Many of these tests are labor intensive and custom in nature. Always discuss the need for specialized analysis with the SLTC prior to collecting or sending samples.

Appendix D discusses techniques for combustible dust sampling. Such sampling is conducted where the potential for rapid combustion/burning (deflagration) or violent burning with rapid release of pressure (explosion) is suspected due to the presence of accumulations of settled dust. Bulk samples of settled dust are collected and sent to the SLTC. Lab analysis is used to determine whether the composition of the dust poses an explosion hazard.

II. Basics of Skin Exposure

A. Effects on the Skin

Skin contact with chemicals can result in irritation, allergic response, chemical burns, and allergic contact dermatitis. Irritant dermatitis may be caused by a variety of substances such as strong acids and bases (primary irritants). Some examples of chemicals which are potent irritants include: ammonia, hydrogen chloride, and sodium hydroxide. Generally, primary irritants produce redness of the skin shortly after exposure with the extent of damage to the tissue related to the relative irritant properties of the chemical. In most instances, the symptoms of primary irritation are observed shortly after exposure; however, some chemicals produce a delayed irritant effect because the chemicals are absorbed through the skin and then undergo decomposition within aqueous portions of the skin to produce primary irritants. Ethylene oxide, epichlorohydrin, hydroxylamines, and the chemical mustard agents, such as bis (2-chloroethyl) sulfide, are classic examples of chemicals which must first decompose in the aqueous layers of the skin to produce irritation.

Allergic contact dermatitis, unlike primary irritation, is caused by chemicals which sensitize the skin. This condition is usually caused by repeated exposure to a relatively low concentration chemical which ultimately results in an irritant response. Frequently, the sensitized area of skin is well defined, providing an indication of the area of the skin which has been in contact with the sensitizing material.

A wide variety of both organic and inorganic chemicals can produce contact dermatitis. Some examples of these chemicals include: aromatic nitro compounds (e.g., 2,4-dinitrochlorobenzene), diphenols (e.g., hydroquinone, resorcinol), hydrazines and phenylhydrazines, piperazines, acrylates, aldehydes, aliphatic and aromatic amines, epoxy resins, isocyanates, many other organic chemicals, and metals (e.g., hexavalent chromium). These substances can also produce contact sensitization. Allergic contact dermatitis is present in virtually every industry, including agriculture, chemical manufacturing, rubber industry, wood, painting, bakeries, pulp and paper mills, healthcare and many others. Also associated with both irritant and allergic contact dermatitis are metalworking fluids (see OSHA's Safety and Health Topics page on Metalworking Fluids).

Lastly, there is a class of chemicals which can produce allergic reactions on the skin after exposure to sunlight or ultraviolet (UV) light. These chemicals are called photosensitizers. Polynuclear aromatic compounds from coke ovens and the petroleum-based tars are examples of chemicals which can be photoactivated on the skin to cause an irritant response.

B. Skin Absorption

In addition to the effects that chemicals can directly have on the skin, the skin also acts as a pathway for chemicals to be absorbed into the body. The skin primarily consists of two layers—the epidermis and the dermis. The outer layer of the epidermis is composed of a compacted layer of dead epidermal cells called the stratum corneum which is approximately 10 − 40 micrometers thick. The stratum corneum is the primary barrier for protection against chemical penetration into the body. Its chemical composition is approximately 40 percent protein, 40 percent water, and 20 percent lipid or fat. Because skin cells are constantly being produced by the body, the stratum corneum is replaced by the body approximately every two weeks.

Chemical absorption through the stratum corneum occurs by a passive process in which the chemical diffuses through this dead skin barrier. Estimates of the amount of chemicals absorbed through the skin as discussed below assume that the chemicals passively diffuse through this dead skin barrier and are then carried into the body by the blood flow supplied to the dermis.

A number of conditions can affect the rate at which chemicals penetrate the skin. Physically damaged skin or skin damaged from chemical irritation or sensitization or sunburn will generally absorb chemicals at a much greater rate than intact skin. Organic solvents which defat the skin and damage the stratum corneum may also result in an enhanced rate of chemical absorption. If a chemical breakthrough occurs while wearing gloves or other protective clothing, the substance becomes trapped against the skin, leading to a much higher rate of permeability than with uncovered skin. A worker who wears a glove for an extended period of time experiences enhanced hydration to the skin simply because of the normal moisture which becomes trapped underneath the glove. Under these conditions, chemical breakthrough or a pinhole leak in a glove can result in greater chemical absorption due to increased friction, contact time with the substance and increased temperature resulting in a higher overall absorption through the skin. In another example, a worker may remove a glove to perform a task which requires increased dexterity, exposing the skin to additional chemical exposure even after redonning the glove.

C. Risk Assessment (Establishing a Significant Risk of Skin Exposure)

Risk is determined from the degree of hazard associated with a material, together with the degree of exposure. Note that dermal exposures may vary widely between workers based on individual hygiene practices. The dermal hazard can be ranked based upon the degree of skin damage or systemic toxicity associated with the chemical of interest. Those settings with both a high degree of potential exposure and a high degree of dermal hazard would warrant the closest attention, and justify collecting sampling data to document the potential exposure, such as wipe sampling, skin sampling, or biological monitoring.

In estimating the potential exposure, consider the following:

• The risk of chemical splash.
• Significant differences in work practices between individuals.
• Use of gloves versus hand tools when in direct contact with chemicals.
• Use of shared tools.
• Cleaning frequencies for tools and equipment, including doorknobs, telephones, light switches, keyboards and actuators on control panels.

The dermal exposure potential can be ranked based upon the:

• Frequency and duration of skin contact.
• The amount of skin in contact with the chemical.
• The concentration of the chemical.
• The likely retention time of the material on the skin (e.g., highly volatile or dry powdery materials are not likely to remain in contact with the skin, whereas materials with a higher molecular weight and sticky materials will remain in contact with the skin and thus be available for dermal exposure).
• The potential for dermal absorption, as described below.

The absorption of chemicals through the skin can have a systemic toxic effect on the body. In certain instances dermal exposure is the principal route of exposure, especially for chemicals which are relatively non-volatile. For example, biological monitoring results of coke oven workers coupled with air monitoring of the workers' exposure demonstrated that 51 percent of the average total dose of benzo[a]pyrene absorbed by coke oven workers occurred via skin contact (VanRooij et al., 1993). Studies of workers in the rubber industry suggest that exposure to genotoxic chemicals present in the workplace is greater via the skin than via the lung (Vermeulen et al., 2003).

Dermal exposures will contribute significantly to overall exposure for those chemicals with low volatility and high dermal penetration, such as many pesticides. One indicator of the volatility of a chemical is the Vapor Hazard Ratio (VHR). The VHR is the ratio between the vapor pressure (at a given temperature and pressure) and the airborne exposure limit for a chemical; the lower the VHR, the less significant the airborne exposure to vapor and the greater the potential for dermal penetration.

A common indicator of dermal absorption potential is the relative solubility of a material in octanol and water, often called the octanol-water partition coefficient (K_ow). This partition coefficient is often expressed in the logarithmic form as Log K_ow. Chemicals with a log K_ow between -0.5 and + 3.0 are the most likely to penetrate the skin (Ignacio and Bullock, 2006). Chemicals must have some degree of lipid (fat) solubility to absorb into the stratum corneum. To penetrate into thelayer of skin, they must have some degree of solubility in water.

Note also that skin penetration may be increased under conditions of high humidity. When temperatures are elevated, sweating may contribute to increased skin absorption. Wearing ineffective or compromised gloves, for example, may actually increase dermal penetration. Proper selection and maintenance of chemical protective gloves, as required by the PPE standard (29 CFR 1910.132), are essential to ensure effective protection. Subsection E provides additional information regarding glove permeability.

Chemicals for which dermal exposures are recognized as making a significant contribution to overall worker exposure include pesticides, formaldehyde, phenolics, coal tar, creosote, and acrylamide in grouting operations.

Appendix A lists chemicals with systemic toxicity for which skin absorption is recognized as making a significant contribution to occupational exposure. This list includes only chemicals that have OSHA PELs or ACGIH TLVs and a "skin designation" or "skin notation," and is not intended to be a comprehensive list. This exposure may occur by contact with vapor, aerosols, liquid, or solid materials, and includes contact with the skin, mucous membranes and the eyes. Where high airborne concentrations of vapor or aerosol occur involving a chemical noted for dermal absorption, the issue of exposed skin should be considered carefully. Note also that certain chemicals, such as dimethyl sulfoxide (DMSO) are known to facilitate dermal absorption of other chemicals.

For chemicals which are absorbed through the skin and which are hazardous, the levels of exposure on the skin must be maintained below a level at which no adverse effects would be observed. One of the simplest ways of determining this amount is to estimate the amount of a chemical which can be absorbed into the body based upon an air exposure limit. For example, the OSHA permissible exposure limit (PEL) for methylenedianiline (MDA) is 0.1 parts per million (ppm), or 0.81 milligrams per cubic meter of air (mg/m³). If we assume that the average worker breathes 10 m³ of air in an eight-hour workday, and further assume that all of the MDA is absorbed from the air at the PEL, then the maximum allowable dose to the body per workday becomes:

(0.81 mg/m³) x (10 m³) = 8.1 mg maximum allowable dose to the body for MDA

In addition to using OSHA PELs, ACGIH TLVs or other occupational exposure limit (OEL) can also be used to establish the maximum allowable dose in the same manner. This method assumes that the toxic effects of the chemical are systemic and that the toxicity of the chemical is independent of the route of exposure. Note that the concept of a maximum allowable dose cannot be used to enforce compliance with the OSHA PELs for air contaminants (29 CFR 1910.1000) through back-calculation of a measured dermal exposure.

The lethal dose to the skin which results in death to 50 percent of exposed animals (LD₅₀ dermal) is also a useful comparative means of assessing dermal exposure hazards. The OSHA acute toxicity definition (defined in 29 CFR 1910.1200 Appendix A, Section A.1.1) as it relates to skin exposure refers to those adverse effects that occur following dermal administration of a single dose of a substance, or multiple doses given within 24 hours. Substances can be allocated to one of four acute dermal toxicity categories according to the numeric cut-off criteria specified in Table 1 below. Acute toxicity values are expressed as approximate LD₅₀ dermal values or as acute toxicity estimates or ATE (see Appendix A of 29 CFR 1910.1200 for further explanation on the application of ATE. Refer to Table A.1.2 in Appendix A for Conversions to ATEs).

If available, the no observable effect level (NOEL) can also be useful in establishing a safe exposure level. Skin notations or skin designations for chemicals listed with ACGIH TLVs or the OSHA PELs are also useful guides; however, many chemicals (e.g., hexone, xylene and perchloroethylene) which can pose a dermal hazard are not designated.

D. Estimating the Extent of Absorption of Chemicals Through Skin

For exposure to chemicals which are recognized as systemic toxins, that is, chemicals which are toxic once absorbed into the bloodstream, the route of exposure to the chemical may not be important. Hence, the maximum allowable dose can be used as a basis for determining if a chemical poses a skin exposure hazard.

The extent of absorption of a chemical through the skin is a function of the area of the exposed skin, the amount of the chemical, the concentration of the chemical on the skin, the rate of absorption (flux rate) into the skin, and the length of time exposed (Kanerva et al., 2000). Assume, for example, that a worker has contact on the interior portion of both hands to a solution of phenol (10 percent solution by weight) for two hours. Approximately how much phenol would be absorbed? The flux rate, J, is determined by:

J = (K_p) (Concentration of Chemical on Skin)

Where K_p is skin permeability coefficient of compound in water (cm/hr)

Kp for phenol = 0.0043 cm/hr (K_p values are available in the EPA Dermal Risk Assessment Guide; EPA/540/R/99/005, 2004)

Thus, at a concentration of 10 percent by weight (10 g/100 cm³; 10,000 mg/100 cm³; or 100 mg/cm³ where 1 cm³ of water weighs 1 g and 1 g equals 1,000 mg):

J = (0.0043 cm/hr) x (100 mg/cm³) = 0.43 mg/(cm²•hr)(flux rate)

Hence, under these conditions, 0.43 mg of phenol will be absorbed through the skin per cm² of exposed skin per hour.

Therefore, the absorbed dose of phenol through the skin of a worker's two hands (both hands exposed with an approximate area of 840 cm²) would be determined as follows:

Absorbed Dose = (840 cm²) x (0.43 mg/( cm²•hr)) (2 hr) = 722 mg absorbed over a two-hour period.

This compares to an allowable dose (PEL = 19 mg/m³) via the lung for an eight-hour exposure of 190 mg [(19 mg/m³) x (10 m³)]. Hence, this two-hour exposure via the skin would represent absorption of phenol which is 3.8 times the allowable dose via the lung.

The following hypothetical example illustrates the relative importance of skin absorption as a factor in exposure. Let us assume that a worker is wearing gloves and the gloves are exposed to a phenol solution. Let us further assume that the penetration through the gloves is detected by a hand wipe sample, and that 75 mg of phenol is reported present from a water hand rinse of the worker's hands taken before lunch. Let us further assume that the amount of phenol detected inside the glove at the lunch break represents a uniform constant exposure which occurred shortly after the beginning of the work shift. Finally, let us further assume that the 75 mg of phenol is present in approximately 10 milliliter (mL) of water (perspiration) present on the surface of the skin. How much phenol was absorbed in the eight-hour period?

First, we determine the flux rate: J = (0.0043 cm/hr) x (75 mg/10 cm³) = 0.0322 mg/(cm²•hr) (flux rate)

Absorbed Dose = (840 cm²) x (0.0322 mg/(cm²•hr)(8 hr) = 216 mg of phenol absorbed

Hence, the estimated amount of phenol absorbed into the body is greater than the maximum dose of phenol permitted to be absorbed via the lung, which is 190 mg.

E. Glove Permeability

Permeation is the process by which a chemical moves through a protective clothing material on a molecular basis. This process includes the: 1) Sorption of molecules of the chemical into the contacted (challenge side) surface of the test material; 2) Diffusion of the sorbed molecules in the material; and 3) Desorption of the molecules from the opposite (collection side) surface of the material. Glove manufacturers publish breakthrough data which reflect the length of time which occurs before a chemical permeates through a particular type of glove material. These tests are performed using American Society for Testing and Materials (ASTM) Method F739 (Standard Test Method for Permeation of Liquids and Gases through Protective Clothing Materials under Conditions of Continuous Contact) in which a pure or neat chemical is placed on one side of a section of the glove material and the time it takes to penetrate through the glove material is measured by analyzing the air on the other side of the glove material to detect chemical breakthrough. ASTM F739 measures the initial breakthrough of the chemical through the glove material (normalized or standardized as a rate of 0.1 μg/cm²/minute) and the rate of permeation. The cumulative amount of chemical that permeates can also be measured or calculated.

Unfortunately, these breakthrough times can be misleading because actual breakthrough times will typically be less than reported by the manufacturer. This is the case because permeation rates are affected by temperature (as temperature increases, permeation rates increase) and the temperature of skin is greater than the test temperature, resulting in an increased permeability rate. Secondly, glove thinning occurs along pressure points where a worker may grip a tool or otherwise exert pressure on an object while wearing a glove. Glove degradation and reuse of gloves can also dramatically reduce a glove's impermeability to chemicals. Additionally, only limited breakthrough data for solvent mixtures is available and in many cases the breakthrough time for a solvent mixture is considerably less than would be predicted from the individual breakthrough times for each of the individual solvent components. Finally, batch variability can also result in wide variations in breakthrough times from one glove to the next (Klingner and Boeniger, 2002). Further, it is difficult to generalize glove breakthrough data from one manufacturer to the next, or even between one model of glove and another from the same manufacturer. This is particularly true for disposable gloves, since different fillers may be used in the formulation of different gloves, resulting in different breakthrough performance.

As a result of these limitations, it is necessary that the employer evaluate glove selection and use to prevent worker exposure as specified in 29 CFR 1910.132(d). Guidance on conducting in-use testing methods for glove selection is available (Boeniger and Klingner, 2002).

III. Wipe Sampling, Field Portable X-Ray Fluorescence Sampling, Dermal Sampling and Biological Monitoring

A. Surface Wipe Sampling

Surface wipe sampling is conducted to assess the presence of a contaminant on surfaces in the workplace that may lead to worker exposure. Surfaces contaminated with a hazardous liquid, particles, or dried residue may be contacted by workers, leading either to dermal exposure or transfer to foodstuffs and accidental ingestion. Settled dusts containing toxic material may be disturbed and resuspended, resulting in inhalation exposure.

In instances where surface contamination is suspected and the employer has not required the use of effective PPE for workers in these areas, wipe sampling may be an effective means of documenting that a skin hazard exists. Wipe sampling can help establish that a significant amount of surface contamination is present in areas in which workers are not effectively protected by PPE. Wipe samples taken inside the sealing surface of "cleaned" respirators can establish the absence of an effective respiratory protection program.

In areas where exposures to toxic metals such as lead (Pb) occur, wipe sampling of settled dust can demonstrate that a reservoir for potential exposure exists; resuspension of such settled dusts can lead to inhalation exposure. This is particularly true if improper housekeeping techniques are used, such as: dry sweeping; blowing off surfaces with compressed air; or using a shop vac instead of a HEPA-rated vacuum cleaner.

In break areas, the presence of surface contamination can lead to contamination of foodstuffs and hence, accidental ingestion of toxic material. The same is true for contamination on drinking fountains. Contamination found on the clean side of a shower or locker area could suggest the potential for take-home contamination, resulting in additional toxic exposures occurring while away from work. All of these types of wipe sampling results can be used to support violations of the housekeeping requirements found in the expanded health standards in Subpart Z of 29 CFR 1910.

In many instances, several wipe samples taken in an area suspected of being contaminated may be useful. For example, some surfaces which would be expected to be contaminated with chemicals because of airborne deposition of a non-volatile chemical may actually be relatively free of surface contamination because of frequent contact of the surface by workers (i.e., frequently contacted surfaces may be expected to be "clean" because of contaminant removal by frequent worker contact). Wipe samples of frequently contacted surfaces in conjunction with less frequently contacted surfaces in the same vicinity can be useful to establish the likelihood that skin exposure is occurring in "clean" areas in which PPE is not being used, or is being improperly used.

Housekeeping deficiencies may also be demonstrated by wipe samples which show major differences in surface contamination between work areas that have been routinely cleaned and areas which have not been recently cleaned. This sampling would allow the CSHO to demonstrate the employer's failure to maintain a clean work area. A reference control wipe sample or samples taken from areas in which exposure is not anticipated will also help to establish the relative amount of surface contamination.

Surface wipe sampling can be conducted qualitatively, for example, wiping irregular surfaces such as a doorknob, tool handle or faucet handle, or quantitatively, in which an area of specified size is wiped. Wiping an area of a specified size is necessary to determine the concentration of a contaminant on a surface. This is needed for estimating the amount of contamination to which workers are potentially exposed. The customary size of the surface area to be wiped is a 10 cm x 10 cm square, i.e., 100 cm². The 100 cm² value approximates the surface area of a worker's palm. Thus, the amount of contaminant in a 100 cm² sample could all be transferred to a worker's hand upon contact.

In industries such as the pharmaceutical industry, a common rule of thumb is to use the maximum allowable dose (based on the chemical's airborne exposure limit in units of μg/m³) and the approximate area of a worker's hand (100 cm²) to arrive at an acceptable value for surface contamination in work areas (i.e., a housekeeping standard). For example, if the eight-hour TWA exposure limit for a chemical is 1 μg/m³, the maximum allowable dose for that chemical is 10 μg. As noted in Section II.C., the chemical's eight-hour time-weighted average (TWA) airborne exposure limit is multiplied by 10 m³, the volume of air inhaled by an average worker in an eight-hour workday, to determine the maximum acceptable dose (i.e., 1 μg/m³ x 10 m³ = 10 μg). The maximum acceptable dose is then divided by the area of a worker's hand to determine the acceptable surface limit of 10 μg/100 cm² or 0.1 μg/cm². By this rule of thumb, the amount of contaminant picked up by one hand contacting the contaminated surface is equivalent to the toxic dose allowed by the eight-hour TWA airborne exposure limit (determined by multiplying by the 10 m³ of air breathed by an average worker in an eight-hour workday).

For highly toxic materials, hazardous levels of surface contamination will often be invisible to the unaided eye, while limits of detection for wipe sampling will be considerably more sensitive. For example, the limit of visible residue for active pharmaceutical ingredients is typically 1–5 μg/cm², whereas good surface wipe sampling techniques can have limits of detection in the low nanogram range. This underscores the essential value of surface wipe sampling in areas where highly toxic materials such as lead or chromium (VI) are present.

B. Field Portable X-Ray Fluorescence Sampling

X-ray fluorescence (XRF) provides real-time measurements of elemental metal on surfaces. This may be useful to measure metal in settled dust on contaminated surfaces, or in surface coatings such as on painted metal or wood. A real-time XRF analyzer and operator are available from the Health Response Team. XRF uses the interaction of x-rays with a target material to determine the elements present and their relative concentrations. When the target material has been excited by being bombarded with high-energy x-rays (or gamma rays), the material emits secondary or fluorescent x-rays that are characteristic of each element present. The rate of generation of the emitted fluorescent x-rays is proportional to the elemental concentration and is used to quantify the results.

Because x-rays will penetrate an object, the XRF will detect metals both on the surface and within the substrate of the material. To determine the quantity of removable metal contamination on a work surface, a reading is first taken on the uncleaned surface. The surface is then cleaned with a metal removal wipe until all visible dust, dirt, and debris is removed. After cleaning, a second reading is taken at the same spot and its value is subtracted from the initial reading to determine the surface concentration of metals.

The same sampling and citation strategies used for wipe sampling apply to XRF sampling. The advantage of XRF over wipe sampling is its rapid (approximately one minute per reading) sampling rate and the real-time results. For laboratory confirmation of XRF results, the area sampled with the XRF can be wipe-sampled using the traditional methods described in this chapter and submitted to the SLTC for analysis.

C. Dermal Sampling

Skin sampling is used to estimate the amount of material which contacts the skin and is relevant both for materials that affect the skin, such as corrosive materials, and for materials which absorb through the skin and have systemic effects.

Dermal exposure may be assessed through either direct or indirect methods. Direct methods measure the amount of material which contacts the skin, for example, through wipe tests which remove and recover the material from exposed skin, or use of sorbent patches (dosimeters) which are placed over the skin and capture material which would have contaminated the skin. Indirect methods measure the amount of contaminant that enters the body. Indirect methods are also known as biological monitoring.

D. Biological Monitoring

Biological monitoring is used to assess uptake into the body of a contaminant of concern. Biological monitoring is defined by the American Industrial Hygiene Association Committee on Biological Monitoring as "the assessment of human exposure through the measurement of internal chemical markers of exposure, such as the chemical agent itself and/or one of its metabolites or an exposure related biochemical change unrelated or related to disease, in human biological samples" such as urine, blood, or exhaled breath (AIHA, 2004). Biological monitoring by itself does not indicate the route of exposure to the material. Airborne sampling, skin sampling, and/or surface sampling would be needed to pinpoint the source of exposure.

Biological monitoring can be a useful technique for determining if dermal exposure is a significant contributor to the worker's overall exposure. For example, in a work environment in which the air exposure to a specific chemical is well controlled, an abnormally elevated biological monitoring result will likely indicate that skin or ingestion is a major mode of exposure. Coupled with evidence of surface contamination, and documentation of poor or non-existent personal protection against chemical skin exposure, biological monitoring can be a valuable means of documenting dermal exposure to a chemical. Biological monitoring could also be used to assess the effectiveness of PPE, such as chemical protective clothing or gloves, or the effectiveness of cartridge change schedules for air-purifying respirators. Prior to conducting biological monitoring, determine the variables that may affect the results including the potential for interferences (e.g., diet, over-the-counter drugs, personal care products, existing medical conditions, other).

Biological monitoring data can hypothetically be used to back-calculate an estimate of the corresponding airborne exposure that would have resulted in observed biological exposure. This requires the availability of adequate exposure modeling for the toxic material of interest. For example, this is done in cases of overt carbon monoxide poisoning, as described below in Section IV.C.1.

Biological monitoring by itself does not indicate that a toxic or adverse health effect has occurred, only that the material has entered the body. Biological exposure guidelines, such as the ACGIH BEIs, are numerical values below which it is believed nearly all workers will not experience adverse health effects. Where measured levels exceed a BEI, this finding provides evidence that exposures have occurred which can result in an adverse health effect. Further, a number of the OSHA expanded health standards in Subpart Z contain biological monitoring provisions. Appendix B summarizes the 2012 ACGIH BEIs and the biological monitoring guidelines contained in the OSHA expanded health standards.

In addition, NIOSH offers guidance for biological monitoring, which may be found at the following link: NIOSH Biological Monitoring Summaries. The NIOSH Biomonitoring Summaries provide a brief overview of the usage, environmental pathways, sources of exposure, toxicology, health effects, and human exposure information for most of the chemicals or chemical groups evaluated in the National Report on Human Exposure to Environmental Chemicals.

Finally, there are many studies in the peer-reviewed literature that report exposure levels for numerous chemicals measured as biological matrices for workers in a variety of occupations and industries. These studies can be useful, in a comparative fashion, for assessing the extent of exposure between exposed and unexposed workers when the workplace in the study involves the same conditions (e.g., chemical exposure, type of work) as the workplace being inspected.

IV. Sampling Methodology

A. Surface Wipe Sampling

The most common surface testing technique is surface wipe sampling. The Chemical Sampling Information (CSI) file contains wipe sampling information for many of the chemicals regulated by the expanded health standards, including the type of wipe to use.

Frequently, the wipe is dipped in distilled water or other suitable solvent prior to wiping the surface of interest. This technique facilitates transfer of the contaminant from the surface to the wipe. It is best to use a minimum of water/solvent on the wipe so that all of the water/solvent will be picked up by the wipe and not left behind on the sampled surface.

The percent recovery of the contaminant of interest from the sampled surface may vary with the characteristics of the surface sampled (e.g., rough or smooth), the solvent used, and the technique of the person collecting the sample. Consequently, surface wipe sampling may be only semi-quantitative. No OSHA standards currently specify acceptable surface limits. Results of surface wipe sampling are used qualitatively to support alleged violations of housekeeping standards and requirements for cleanliness of PPE. Enforcement guidance is described in more detail in Section VI.

Templates may be used to define a relatively constant surface area for obtaining a wipe sample, but are not always helpful. Templates can only be used on flat surfaces, and they can cause cross-contamination if the template is not thoroughly cleaned between each use. Constructing single-use 10-cm x 10-cm templates is recommended (e.g., using cardstock or file folders). The CSHO may want to sample a much larger surface area than the area covered by a template (e.g., the CSHO may want to determine the cleanliness of a lunch table or other large surface area). In all cases, the CSHO should measure the dimensions of the area being sampled and record this value on the OSHA Information System (OIS) sampling worksheet because the mass amount of chemical measured by the laboratory will be used to determine the mass per unit area for the wipe sample.

Appendix C provides general procedures for collecting surface wipe samples, including wipe sampling procedures for hexavalent chromium.

Other surface testing techniques include direct-reading swab and wipe tests and vacuum dust collection to collect bulk samples of dust for analysis. Swab and wipe test kits with colorimetric indicators are available for contaminants, including lead, chromate, cadmium, amines, aliphatic and aromatic isocyanates, and others. These nonquantitative assessments can be used to provide an immediate indication in the field of the presence of a contaminant on a surface or the general level of surface contamination. The presence of contamination can be used to provide evidence for housekeeping deficiencies.

Lead, chromate and other test swabs are self-contained units with a fiber tip at one end and glass ampoules with reactive materials inside the swab barrel. The swabs are activated by squeezing at the crush points marked on the barrel of the swab, shaking well to mix the reagents, and then squeezing until the reactive liquid comes to the tip of the swab. While squeezing gently, the tip of the swab is rubbed on the surface to be tested for 30 to 60 seconds. The tip of the swab turns color in the presence of the chemical (for example pink to red for lead and pink to purple for chromates). Color development depends on the concentration of chemical present. Potential limitations associated with swabs include:

• Interferences in color development from chemicals or other materials that may be present (e.g., dark colored dust or dirty surfaces obscuring color development on the lead swab tip; rubbing too long or too hard causing a metallic film to collect on the lead swab tip which obscures the color change; bleeding occurring on the lead swab tip when the test surface is painted red; and high concentrations of mercuric chloride or molybdate interfering with the color development of chromate swabs).
• Delayed results (e.g., up to 18 hours for the detection of lead chromate in marine and industrial paints).
• Destruction or damage to the testing surface to assess multiple layers on metal parts or painted surfaces.

Contact the SLTC to discuss wipe sampling before considering use of these methods.

B. Skin Sampling Methods

Skin sampling methods are classified as "interception" and "removal" methods. Interception methods use a "dosimeter" such as a sorbent pad placed on the skin or clothing, which "intercepts" the contaminant before it reaches the skin. After the exposure period ends, the dosimeter is removed, and either extracted in the field to recover and stabilize the analyte of interest, or sealed and sent for laboratory analysis to determine the mass of contaminant collected on the pad. In some cases, direct reading pads are available which undergo a colorimetric change when exposed to the contaminant of interest.

"Removal" methods remove the contaminant of interest after it has deposited on the skin. Either the skin is rinsed with distilled water or mild washing solution and the rinsate is collected and analyzed for the contaminant of interest, or the skin is wiped with a dry or wetted wipe, and the analyte of interest is then extracted from the wipe. One approach is to place the hands inside a bag that is partially filled with the washing solution, such as distilled water, distilled water with surfactant, or isopropanol diluted with distilled water. The hand is then dipped in the solution and shaken a specified number of times to recover the contaminant from the hand.

Both of these types of methods are generally qualitative in nature. The percent recovery may be variable or not quantitatively established. Further, no OSHA standards currently specify quantitative limits for dermal exposure. Qualitative documentation of the presence of a contaminant on the skin is sufficient to determine whether PPE is inadequate, whether due to inappropriate selection, maintenance, or cleaning.

When considering dermal sampling, consult OSHA's webpages at the following link: Dermal Dosimetry.

1. Direct Reading Patches/Charcoal Felt Pads

   In some instances, direct reading patches and/or bandage-type patches can be worn inside a glove to demonstrate directly through a color change that an exposure has occurred. In other instances, charcoal felt patches or bandages can be worn which can be analyzed by a laboratory to establish the presence of glove permeation by volatile organic chemicals. These charcoal pads may also be used for detection of less volatile organic chemicals. However, poor sample recoveries from a charcoal surface for higher molecular weight substances may result in underestimating the extent of skin exposure for these types of chemicals.

   When sampling inside a glove, OSHA recommends that workers being sampled wear disposable gloves inside their normal PPE, with the indicator/charcoal felt pads being placed on the disposable glove surface. Placing the pad on the disposable glove between the skin surface and the regular PPE eliminates any potential skin exposure from the chemicals used in the colorimetric pads, and also reduces any effects that perspiration might have on the sampling pads.

   For inside-the-glove sampling, it also is advisable to use a control pad to measure the concentration of airborne volatile chemicals. This control pad should be attached to the worker's clothing while the worker performs his/her normal tasks. The glove sample result would then be corrected for the amount of the organic chemical in the airborne sample to determine the amount of organic chemical actually permeating the protective glove relative to the amount of organic chemical entering the glove opening. This procedure, therefore, would allow the sampler to identify the possible route of glove contamination.

2. Wipe Sampling of Skin

   Skin wipe samples taken on potentially exposed areas of a worker's body are a useful technique for demonstrating exposure to a recognized hazard. For water-soluble chemicals, a wipe pad moistened with distilled water can be used to wipe the skin. Generally, the best procedure is to allow workers to use the wipe pad to clean their skin surfaces, and then have them insert the wipe pad into a clean container, which is labeled and sealed. Hands, forearms, faces, and possibly feet may be exposed to contaminants that a wipe sample of the skin can be used to establish exposure. Include a blank water sample and use only distilled water, or another source of water approved by the laboratory, for analysis purposes.

C. Biological Monitoring Methodology

In the event that a CSHO believes biological monitoring would be valuable to assess and evaluate worker exposure to a substance or mixture of substances, he or she should first contact their Regional Office, the SLTC and the Office of Occupational Medicine to determine the most effective approach and technique to obtain the desired result. Biological sampling requires special consideration and will be addressed on a case-by-case basis.

Biological monitoring results can be used to demonstrate significant skin absorption, ingestion or airborne exposures. For instance, when wipe/skin sampling has indicated exposure, a voluntarily obtained worker biological sample may prove useful in documenting that skin exposure to the chemical of concern has occurred. Ideally, it is desirable to have samples from a number of workers who are suspected of being exposed. Also, control samples from individuals who do not have skin exposure, or are suspected of much less exposure, are valuable. Note that skin sampling conducted just prior to biological monitoring may result in decreased biological uptake.

1. Carboxyhemoglobin Evaluation

   Biological monitoring can also be used to estimate the degree of exposure after an emergency. Table 2 shows the relationship between airborne carbon monoxide (CO) concentrations and steady state carboxyhemoglobin (COHb) levels.

   Table 2. Carbon Monoxide (CO) Concentration Versus Blood Carboxyhemoglobin (COHb) Levels*

   CO Concentration (ppm)	Steady-State Blood COHb Levels (percent)
   0.1	0.25
   0.5	0.32
   1	0.39
   2	0.50
   5	1.0
   10	1.8
   15	2.5
   20	3.2
   40	6.1
   60	8.7
   80	11
   100	14
   200	24
   400	38
   600	48
   800	56
   1,000	61
   *Predicted using the Coburn-Forster-Kane (CFK) model. Source: ATSDR, 2009

   Post-exposure COHb measurements can be used to back-calculate airborne CO concentrations in order to determine whether a citation is warranted. COHb values provided by a non-OSHA medical professional are submitted to the SLTC for evaluation using a special algorithm online worksheet on the OSHA Intranet. COHb values may be determined either from a blood sample, a breath analyzer, or a Pulse CO-OximeterTM finger measurement. No physical samples are sent to the SLTC, but chain-of-custody must be documented in the OIS.

   The SLTC employs a modified, more accurate version of the Coburn-Forster-Kane equation than the closed-form version used in the 1972 NIOSH Criteria Document. The SLTC equation calculates the eight-hour TWA. Poisoning cases generally involve levels above five percent COHb. The calculation also provides an incident-specific sampling and analytical error designed to deal with the uncertainties in the data. The calculation is performed at the SLTC and the results are critically assessed for accuracy by the SLTC staff prior to reporting. The SLTC carbon monoxide experts are available to assist CSHOs in acquiring data and in interpreting results.

   The following are suggestions to help ensure that the most accurate calculations will be performed.

   • Before going on site, download, print and read the Carbon Monoxide Worksheet ("Submitting Data for the Carbon Monoxide Calculation at the OSHA Salt Lake Technical Center (SLTC)") on the OSHA Intranet. Take the worksheet to the site.
   • If possible, call one of the SLTC carbon monoxide experts before going to the site, especially if methylene chloride is used. The Carbon Monoxide Worksheet lists the SLTC contact persons on the worksheet.
   • Collect vital statistics for the victim(s) (age, weight, sex, living or deceased).
   • Detail smoking activity (first-hand, second-hand tobacco smoke).
   • Document oxygen saturation-affecting conditions such as pre- and post-exposure activity levels and oxygen therapy.
   • Provide accurate timelines (how long the worker was exposed, when the worker was removed, how long resuscitation was performed, the time between removal and when the COHb was taken, etc.).
   • List signs and symptoms of suspected exposure.
   • Review the document for accuracy and completeness before submitting it to the SLTC.
2. Hydrogen Sulfide

   For evaluation of suspected hydrogen sulfide (H2S) overexposures, blood thiosulfate monitoring is recommended (Ballerino-Regan and Longmire, 2010).  Blood sulfide levels are useful only if obtained within two hours of exposure, and sulfhemoglobin levels are not useful for documenting H2S exposure. Urinary thiosulfate levels are frequently used as a biomarker, however, a quantitative relationship between hydrogen sulfide exposure levels and urinary thiosulfate levels has not been established (ATSDR, 2006). Urine thiosulfate elevation does not occur in the case of rapid fatalities but may be elevated in nonfatally exposed workers. Analysis of COHb may also be useful, since this is a reported metabolite of H2S (NIOSH 2005-110, 2004).

   For biological monitoring, proper sampling containers and a protocol for handling and shipping samples need to be followed. In general, a qualified laboratory which is experienced in the analysis of biological samples will provide sample vials, shipping containers, and the technical expertise to properly collect, store and ship specimens.

3. Review of Employer Biological Monitoring Results

   In instances in which an employer has been conducting biological monitoring, the CSHO shall evaluate the results of such testing. The results may assist in determining whether a significant quantity of the toxic material is being ingested or absorbed through the skin. However, the total body burden is composed of all modes of exposure (e.g., inhalation, ingestion, absorption and injection). For the CSHO to assess the results of the biological monitoring, all the data (including any air monitoring results) must be evaluated to determine the source(s) of the exposure and the most likely mode(s) of entry.

   Results of biological monitoring which have been voluntarily conducted by an employer shall not be used as a basis for citations. In fact, OSHA promotes the use of biological monitoring by employers as a useful means for minimizing exposures and for evaluating the effectiveness of control measures.

   Citations, in consultation with the Regional Office, would be appropriate when biological monitoring results indicate an unacceptable level of exposure, and the employer is unable to demonstrate that meaningful efforts to reduce or control the exposure(s) were taken.

V. Other Analyses

Soil Analysis in Support of the Excavation Standard

Soil analyses at the SLTC is performed to support CSHOs' inspection and compliance responsibilities with respect to trenching and excavation standards such as 29 CFR 1926 Subpart P. It also supports citations and legal proceedings. For further information refer to OSHA's Trenching and Excavation Topic Page.

A representative soil sample from a trench or excavation is sent to the SLTC for analysis. Soil should be placed in a heavy-duty, tear-resistant plastic bag, secured, and sealed with tape to be airtight. Place the first plastic bag in a second heavy-duty plastic bag for additional protection. Sample size can vary from one pint for very fine-grained samples to two quarts for coarse gravel. A typical sample should be approximately one quart and weigh about three pounds. Do not place any sampling documentation in the bag with the soil.

This soil sample is examined and tested according to OSHA Method ID-194. This fully validated method was developed specifically for the OSHA Excavation standard (29 CFR 1926 Subpart P). The required tests take a minimum of four days before results can be provided. The SLTC sample results specify the soil type as well as the textural and structural classification. The soil classification will be Type A, Type B, or Type C, corresponding to the descriptions listed in the Excavation standard (29 CFR 1926 Subpart P, Appendix A). When requested, moisture content can also be provided.

Any questions arising from this analysis can be answered by trained soil experts at the SLTC. This analysis helps CSHOs as well as the inspected establishment personnel understand how to properly protect workers from cave-ins and how to properly evaluate protection measures used to comply with existing regulations.

VI. Enforcement Recommendations

There are currently no surface contamination criteria or quantifications for skin absorption included in OSHA standards. CSHOs should consult OSHA's Field Operations Manual (FOM) for guidance (e.g., see Chapter 4, Section XIV on citing improper personal hygiene practices based on the absorption hazard). The expanded health standards in Subpart Z generally contain housekeeping provisions that address the issue of surface contamination. Exposures to various chemicals are addressed in specific standards for general industry, construction, and shipyard employment. For example:

• Formaldehyde, see 29 CFR 1910.1048 (paragraph (j) contains the housekeeping requirements).
• Methylenedianiline, see 29 CFR 1910.1050 (paragraph (f) provides that regulated areas must be established for areas with dermal exposure potential and paragraph (l) contains housekeeping requirements).
• Acrylonitrile, see 29 CFR 1910.1045 (paragraph (k) provides that surfaces must be kept free of visible liquid acrylonitrile).

The housekeeping provisions are generally the most stringent for the metals, which in solid form may contaminate surfaces and become available for ingestion or inhalation if housekeeping practices are poor. OSHA standards for the following metals contain provisions stating that "surfaces be maintained as free as practicable of accumulations of" the toxic metal and housekeeping requirements such as a prohibition on use of compressed air for cleaning surfaces:

• Arsenic, see 29 CFR 1910.1018 (standard includes strict housekeeping requirements in paragraphs (k) and (m)).
• Lead, see 29 CFR 1910.1025 (standard contains strict housekeeping requirements in paragraphs (h) and (i)).
• Chromium (VI), see 29 CFR 1910.1026 (standard contains strict housekeeping requirements in paragraphs (i) and (j)).
• Cadmium, see 29 CFR 1910.1027 (standard includes strict housekeeping requirements in paragraphs (j) and (k)).

Useful information on dermal exposure standards can be found at Dermal Exposure - OSHA Standards Safety and Health Topics Page.

Despite the lack of specific criteria or quantitative data for use in the enforcement of elevated exposures to surface and skin chemical hazards in the workplace, it is well established that skin exposure and ingestion of chemicals is a significant mode of occupational exposure. In instances in which a hazard can be established which is not addressed in a specific OSHA standard, the compliance officer may consider a 5(a)(1) General Duty Clause citation to address this concern. Use of the General Duty Clause is discussed in the FOM.

In lieu of issuing a 5(a)(1) citation, it is suggested that alternative citations be issued under one or more of the following OSHA standards:

• Sanitation, see 29 CFR 1910.141. In instances where a high degree of surface contamination is evident, or clear evidence exists to establish skin exposure of workers to a recognized hazard, then 29 CFR 1910.141(a)(3) can be cited. That is, the CSHO can establish that the employer has failed to keep the workplace "clean to the extent that the nature of the work allows."
• Hazard Communication, see 29 CFR 1910.1200. 29 CFR 1910.1200(h) can be cited based upon the evidence collected by the CSHO to demonstrate that the employer failed to adequately inform and train workers on the hazards present in the workplace.
• Personal Protective Equipment, see 29 CFR 1910, Subpart I. A specific citation may be issued for deficiencies in PPE under 29 CFR 1910.132, which requires that the employer evaluate the hazards, select proper PPE, and train workers on proper use of the PPE.
• Respiratory Protection, see 29 CFR 1910.134. The respiratory protection standard contains specific cleaning provisions in paragraph (h).
• Occupational Exposure to Hazardous Chemicals in Laboratories, see 29 CFR 1910.1450.
• Paragraph (f) contains the hazard communication requirements to adequately inform and train workers on the hazards present in the laboratory.
• Paragraph (e)(3) specifies occupational safety and health requirements that must be included in the Chemical Hygiene Plan. It also requires the employer to include the measures that will be taken to ensure the protection of laboratory workers.
• Paragraph (a)(2)(ii) requires that any prohibition of eye or skin contact specified in an expanded health standard be observed.

Pertinent standards dealing with construction (29 CFR 1926) and shipyard employment (29 CFR 1915).

VII. Custom Services Provided by SLTC

The following services are available on a case-by-case basis at the SLTC. Concurrence from the Area Director in an email (or via other means) sent to the SLTC management must be received before the SLTC can commit to providing some of these services.

1. Mass Spectrometry

   The mass spectrometry laboratory at the SLTC has a number of unique tools to help CSHOs resolve difficult field sampling and analytical issues. For example, mass spectrometry can be used to identify unknown or suspected organic substances found in industrial processes, indoor air quality complaints, and contaminated water. It can also be used to identify secondary substances that are given off from a heated material (i.e., thermal decomposition products).

   One of the major functions of the mass spectrometry laboratory is identification and confirmation of analytes measured in gas chromatography (GC) analysis performed at the SLTC. The same separation and identification techniques used to confirm the identity of known analytes are also useful to identify an unknown material, investigate possible contamination or batch uniformity in a material from an industrial process, or to check for conformity with a Safety Data Sheet.

   Volatile organic chemicals in contaminated water can be quantitated by several different processes, including purge and trap, equilibrium headspace analysis, or a novel approach involving thermal desorption called "Twister." The "Twister" technology is simple to use and highly sensitive.

   Thermal Desorption/Gas Chromatography/Mass Spectrometry (TD/GC/MS) is also useful for investigation of low-level or transient odors, and indoor air quality-type complaints. The SLTC can provide sampling tubes containing three resin beds designed to collect a broad range of volatile analytes. The entire collected sample is thermally desorbed into the GC column, providing analysis with maximum sensitivity.

   Using a device called a direct insertion probe and a technique called pyrolysis, some thermally labile compounds can be introduced directly into the mass spectrometer source before heat is applied. With another instrument called a PyroprobeTM, materials can be heated to temperatures as high as 1,400°C, with subsequent introduction of decomposition products into the GC column. Products released from materials involved in a fire, heated by a welder or blowtorch, or from any process involving heating can be studied in this way.

2. Materials Analysis

   The SLTC provides a variety of services to determine the cause of materials failure. Materials failure analysis examines the extent to which the properties of materials or their use contribute to significant investigations, including fatalities. This procedure often involves collaboration of experts in multiple disciplines including metallurgical engineering, materials science, explosibility, and both organic and inorganic chemistry.

   The SLTC has assisted in the investigation of several diverse catastrophes. These investigations have included chemical, gas, and dust explosions and disasters caused by incompatible chemicals and processes; metal and plastic failures; wire, synthetic and natural fiber rope failure; scaffold planking failure; plastic, fiberglass and metal piping failure; radio tower support failure; safety equipment failure; and chain and equipment overloading.

   SLTC's services include assistance in searching for industry standards that help support citations, and assistance with finding an accredited laboratory to perform any analysis that is not done at the SLTC. The SLTC tailors the assistance to the particular investigation. The SLTC can either arrange to fully investigate the accident on site, or to review results from an independent laboratory.

3. Sampling for Biological Pathogens

   SLTC provides biological (both organism and chemical by-product) sampling and analysis coordination as a service to CSHOs. The SLTC has developed a standard operating procedure to assure consistent sample handling and analysis. Samples collected and analyzed through this procedure are compliant with the SLTC quality control system and chain-of-custody requirements. SLTC offers contracting services for fungi, bacteria such as Legionella, and endotoxin analysis. Other services can be arranged on a case-by-case basis.

   Again, before collecting samples for microbiological analysis, CSHOs are requested to contact the SLTC for sampling requirements, technical support, assessment, and analytical coordination. The SLTC staff will review sampling and analysis plans with CSHOs and make recommendations where appropriate. The purpose of this process is to ensure that prudent sampling is performed.

4. Explosibility Analysis

   Because of the complexity of this field, it is strongly recommended that CSHOs contact the SLTC before taking explosibility samples. Doing this allows the explosibility experts to assist CSHOs in taking appropriate samples, and in tailoring the analysis to provide support for the specific inspection.

   The SLTC provides an assortment of analytical and technical information services in support of inspections involving potential explosion hazards. Analytical testing is performed in support of OSHA inspections pertaining to hazardous classified locations, grain handling, dust collection systems, confined spaces, and housekeeping. Informational support is offered for litigation, interpretation of analytical results (both in-house testing results and results from contract laboratories), and guidance for sampling and standard applicability. Explosibility experts can help investigate industrial incidents involving explosions. This help may include normal explosibility testing, and research into the reactive nature of the materials in question.

   The SLTC can provide analyses for flash points, energetic reactivity of chemicals, and autoignition temperatures. This testing is useful in support of a wide variety of inspections. Procedures for combustible dust sampling are discussed in detail in Appendix D.

VIII. References

AIHA, 2004. "Biological Monitoring – A Practical Field Manual". American Industrial Hygiene Association (AIHA) Biological Monitoring Committee, Shane Que Hee, Editor. Fairfax, Virginia: AIHA Press.

ATSDR, 2009. "Draft Toxicological Profile for Carbon Monoxide, September 2009". U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry (ATSDR). Available online at: //www.atsdr.cdc.gov/ToxProfiles/tp.asp?id=1145&tid=253. Accessed January 25, 2013.

BLS, 2012. "Workplace Injuries and Illnesses – 2011". Bureau of Labor Statistics, U.S. Department of Labor (DOL) (25 October 2012). Available online at: //www.bls.gov/news.release/pdf/osh.pdf. Accessed January 25, 2013.

Boeniger, M.F. and T.D. Klingner, 2002. "In-Use Testing and Interpretation of Chemical-Resistant Glove Performance". Applied Occupational and Environmental Hygiene 17(5): 368–378.

Boeniger, M.F., 2003. Invited Editorial. "The Significance of Skin Exposure". The Annals of Occupational Hygiene 47(8): 591–593.

EPA, 2004. "Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment)". Publication No. EPA/540/R/99/005; OSWER 9285.7-02EP; PB99-963312. Office of Superfund Remediation and Technology Innovation, U.S. Environmental Protection Agency . Available online at: //cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=183584&inclCol=eco. Accessed January 25, 2013.

Ignacio J.S. and W.H. Bullock (eds), 2006. "A Strategy for Assessing and Managing Occupational Exposures, Third Edition". Fairfax, Virginia: American Industrial Hygiene Association (AIHA) Press.

Kanerva, L., P. Elsner, J.E. Wahlberg, and H.I. Maibach, 2000. "Handbook of Occupational Dermatology". Berlin Heidelberg: Springer-Verlag.

Klingner, T.D. and M.F. Boeniger, 2002. "A Critique of Assumptions about Selecting Chemical-Resistant Gloves: A Case for Workplace Evaluation of Glove Efficacy". Applied Occupational and Environmental Hygiene 17(5): 360–367.

NIOSH 2205-110, 2004. "Specific Medical Tests or Examinations Published in the Literature for OSHA-Regulated Substances". DHHS (NIOSH) Publication No. 2005-110 (December). U.S. National Institute for Occupational Safety and Health. Available online at: //www.cdc.gov/niosh/docs/2005-110/medstart.html. Accessed January 25, 2013.

VanRooij, J.G., M.M. Bodelier-Bade, and F.J. Jongeneelen, 1993 "Estimation of Individual Dermal and Respiratory Uptake of Polycyclic Aromatic Hydrocarbons in 12 Coke Oven Workers." British Journal of Industrial Medicine 50(7): 623–632.

Vermeulen, R., R. Bos, J. Pertijs, and H. Kromhout, 2003. "Exposure Related Mutagens in Urine of Rubber Workers Associated with Inhalable Particulate and Dermal Exposure." Occupational and Environmental Medicine 60(2): 97–103.

Appendix A
Chemicals Noted for Skin Absorption

¹ The chemical abstracts service (CAS) number is for information only. For an entry covering more than one metal compound measured as the metal, the CAS number for the metal is given - not CAS numbers for the individual compounds.

² The OSHA PELs provided under "1910" refer to General Industry, 29 CFR 1910.1000 Table Z-1; "1926" refers to Construction, 29 CFR 1926.55, Appendix A; and "1915" refers to Shipyards, 29 CFR 1915.1000. The PELs are 8-hour time-weighted average (TWA) concentrations unless otherwise noted; a (C) designation denotes a ceiling limit. They are to be determined from breathing-zone air samples. If an entry is only listed in mg/m³, the value is exact; when listed with a ppm entry, it is approximate. "SAME" indicates the value for 1926 and 1915 is equal to that listed for 1910 unless otherwise noted.

³ The ACGIH TLVs are from the ACGIH publication 2012 TLVs^® and BEIs^® Based on the Documentation of the Threshold Limit Values for Chemical Substances and Physical Agents & Biological Exposure Indices. "TWA" refers to 8-hour, TWA concentrations; "STEL" refers to "short-term exposure limit," a 15-minute TWA concentration; "C" indicates ceiling limit; a concentration that should not be exceeded during any part of the working exposure; "I" indicates inhalable fraction (particle aerodynamic diameter ranging from 0 to 100 micrometers; "IFV" indicates inhalable fraction and vapor; "(L)" indicates exposures by all routes should be carefully controlled to levels as low as possible; "P" indicates application restricted to conditions in which there are negligible aerosol exposures; and "R" indicates respirable fraction (particle aerodynamic diameter ranging from 0 to 10 micrometers).

⁴ Values in this column are STEL values unless noted as ceiling limits with a "C" preceding the value.

⁵ See ACGIH 2012 NIC—proposed change to 10 mg/m³ I (TWA) with skin designation.

⁶ ACGIH separates this listing into "hydrogen cyanide" and "cyanide salts," while OSHA does not differentiate between the two. Only the hydrogen cyanide TLV is listed here.

⁷ See ACGIH 2012 NIC—proposed change to 5 ppm (TWA) with skin designation, no STEL.

⁸ See ACGIH 2012 NIC—proposed change to 0.001 ppm IFV (TWA), 0.003 ppm IFV (STEL), skin designation.