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Evaluating Surface Contamination at Hazardous Waste Sites:
Surface contamination sampling is a vital element
of an effective employee monitoring program.
By NINA BAIRD, EARL COOK, AND WILLIAM PERRY
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This article is posted with permission of Stevens Publishing Corp. It
appeared in "Occupational Health & Safety" Vol. 65 No. 1 January 1996.
As the health and safety officer for a hazardous waste site, how do you know that your
efforts to contain contamination are working or that the personal protective equipment
(PPE) chosen for workers is protecting them from exposure to site contaminants? How do you
determine whether your decontamination procedures are effective, whether your housekeeping
procedures are sufficient, and whether existing work zone boundaries are appropriate? If the corporate safety and health manager or an OSHA inspector arrived today, how
would you demonstrate that you have evaluated the effectiveness of these aspects of your
health and safety program in accordance with HAZWOPER, specifically 29 CFR 910.120
(b)(4)(iv)?1
Surface contamination sampling--often overlooked in the design of exposure assessment
programs at hazardous waste sites--is one answer to each of these questions. The results
of surface contamination sampling on decontaminated items or in a clean zone can be used
to document that site health and safety controls are effective or, alternatively, that
they are not working as expected and need modification. Similarly, sampling for surface
contamination on the inner surface of PPE is an effective way to test its adequacy in
preventing dermal exposure.
Surface contamination sampling is a vital element of an effective employee monitoring
program, especially where dermal contamination can be a significant route of exposure
through absorption or ingestion. Even when air monitoring results indicate that airborne
levels of contaminants are within acceptable limits, surface contamination sampling may be
advisable if skin contact with hazardous materials is possible and could contribute to
overall exposure.
Sampling and Analytical Methods
Standard surface contamination sampling involves wiping a surface with a dry or wetted
sampling filter and analyzing the filter contents. Small pieces of equipment, tools, PPE,
or workers' skin can also be evaluated by "washing" the item and analyzing the
wash liquid (see "Guidance from OSHA's Technical Manual: Standard Wipe Sampling
Techniques," page 48). Alternatively, the presence of some contaminants can be
evaluated instantly by touching or wiping the surface or object with direct-reading media,
such as pH sticks or colorimetric pads, or by using direct reading equipment, such as
mercury sniffers or radiation meters, that detect the presence of volatile substances or
ionizing radiation on a contaminated surface.
Chemical analysis of standard surface contamination samples resembles analysis of other
types of industrial hygiene and environmental samples. Filters used in surface sampling
are typically analyzed in an on-site or off-site laboratory, whereas direct-reading
detection media and equipment provide results without laboratory analysis.
Immunoassay test kits, which work like home pregnancy tests, represent a newer
alternative to conventional wipe sampling technology. Collecting surface samples for
immunoassay analysis is similar to standard wipe sampling, but immunoassay analysis is
done very quickly on site, saving considerable time and money. Immunoassay analytical
procedures require limited training and basic skills, such as the use of chemical
reagents. Existing test kits offer sensitivities in the parts per million or parts per
billion range but are currently available for only a limited number of contaminants (see
"New Immunoassay Analytical Methods," page 49). Immunoassay kits for a wider
range of substances should become available in the near future as demand increases.
Interpreting Sample Results
Results of surface contamination sampling are reported in several ways. Laboratory and
immunoassay results may be reported quantitatively as the total amount of contaminant
collected (in micrograms or milligrams) or as the amount of contaminant per area sampled
(micrograms or milligrams per square centimeter). Direct-reading instruments do not lend
themselves to quantification of contaminant levels, but they can be used simply to detect
the presence or absence of a contaminant on the sampled surface. In either case, the
surface contamination values do not represent airborne exposure levels.
OSHA has not established surface contamination limits. Therefore, these sampling
results must be interpreted on a case-by-case or site-specific basis to evaluate the
effectiveness of contaminant control measures and PPE programs.
Surface sampling results should be interpreted against objective criteria established
by the employer for determining cleanliness. To establish these criteria, the employer may
consider such factors as toxicity, the extent to which the contaminant occurs naturally
(i.e., consideration of background levels), the environmental target levels to be achieved
from site remediation, and the ability of sampling and analytical methods to quantify
contaminant levels.
The remedial investigation/feasibility study for the project or the site work plan may
contain information about environmental background or remediation target levels. The
safety and health plan should document criteria for interpreting surface sampling results
and site-specific quantitative surface contamination limits established by site safety and
health management.
Incorporating Surface Contamination Sampling Into The Site Monitoring Program
Incorporating surface contamination sampling into the monitoring program enables safety
and health managers to collect information that air monitoring alone cannot provide
Indeed, where skin may come in contact with hazardous substances, surface sampling is the
only way--aside from biological monitoring--to determine the potential contribution of
surface contamination to an employee's total exposure. The results of this type of
sampling can affect the job hazard analysis, PPE selection, and employee training. Surface
contamination sampling also enables employers to monitor the migration of contaminants
into clean areas and to modify zone boundaries if necessary, in accordance with 29 CFR
1910.(d)(2), which requires that the site control program "shall be modified as
necessary as new information becomes available." Finally, surface sampling enables
the employer to assess and document the adequacy of specific aspects of the safety and
health plan, such as decontamination procedures and PPE selection, in accordance with
1910.120(b)(4)(iv).
The surface sampling program should be part of the written safety and health plan.
Similar to an air monitoring program, the surface sampling program should describe the
sampling methods to be used, the frequency and location of sampling, criteria for
interpreting sampling results, and requirements for re-sampling if corrective action is
necessary. The program should also include site-specific methods for removing surface
contamination detected on surfaces presumed to be clean.
The appropriate frequency of surface contamination sampling depends on the type of
samples being collected and prior sampling results. For example, if equipment
decontamination procedures prove effective during initial evaluation, intermittent surface
sampling is sufficient to ensure ongoing effectiveness of these procedures. More frequent
testing may be necessary, however, if earlier results indicate that existing
decontamination procedures are insufficient or if gradual chemical permeation of PPE is
possible.
Zone boundaries should be monitored intermittently throughout the life of a project,
unless there is reason to believe that contaminants cannot migrate across zone boundaries
and earlier test results indicate appropriate zone designations. In work areas such as
administrative offices that are regularly used by employees considered to be unexposed,
periodic surface sampling should be conducted. This monitoring should be more frequent if
activities change or prior sample results suggest a problem.
Of course, where surface contamination sampling is conducted, affected employees must
be notified of the results, in accordance with OSHA's requirements for employee access to
exposure and medical records, 29 CFR 1910.20. At the conclusion of project activities,
final surface contamination sampling can be used to verify that all equipment and
personnel gear that will be taken off-site--and perhaps reused at another site--are
effectively decontaminated.
The Benefits of Evaluating Surface Contamination
Surface contamination sampling improves site characterization throughout a project and
allows better decision-making with the increased level of information. The effectiveness
of many safety and health procedures can be evaluated with surface sampling. When
effective procedures are used and their performance is documented, potential liabilities
from worker exposure or noncompliance with HAZWOPER requirements are reduced. Surface
contamination sampling results may point to the absence of a hazard and justify a
downgrade in PPE or other control procedures.
Direct-reading media, by providing immediate and visual evidence of surface
contamination, can serve as an effective training tool to improve worker compliance with
safety and health procedures. Current sampling techniques are simple, and new analytical
methods offer the possibility of inexpensive, quantitative, real-time results. Remedial
project managers who want to improve the characterization of safety and health hazards and
ensure that their worker protection program is cost-effective will incorporate surface
contamination sampling into their safety and health programs.
Nina Baird is an occupational safety and health consultant in Silver Spring, Md.
Earl Cook, CIH, is a senior industrial hygienist with the Occupational Safety and Health
Administration's Health Response Team. William Perry, CIH, is a health scientist with the
Occupational Safety and Health Administration's Directorate of Health Standards.
The opinions, findings, and conclusions presented in this article are not necessarily
those of the Occupational Safety and Health Administration. Any mention of products or
materials does not imply endorsement by OSHA.
New Immunoassay Analytical Methods
Using technology similar to that used in drug screening, blood typing, and home
pregnancy tests, immunoassay analysis for environmental contaminants is a promising
development. Immunoassay test kits are generally used for screening purposes, but their
levels of sensitivity and quantification are sufficient for most surface contamination
sampling.
Kits currently marketed for surface contamination sampling are limited to PCB analysis,
but the range of substances detectable by this method should expand rapidly in the next
few years. A wider range of contaminants-- BTEX, PAHs, TNT, pentachlorophenol, and several
pesticides and herbicides--can be analyzed with soil and water immunoassay test kits that
have potential utility for health and safety sampling. For example, contaminated PPE and
small equipment can be "washed" in a sealed container and the wash liquid can be
analyzed with a water sample immunoassay test kit. Similarly, some contaminated surfaces
can be evaluated with soil sample kits; contaminated concrete, for example, can be ground
into mortar and analyzed using an immunoassay soil sample test.
Immunoassay results can be obtained in an hour or less. Current costs per sample are
generally less than $30 (even less when analyzing a larger number of samples), although
the total cost may be higher if a spectrophotometer or other analytical equipment must be
purchased or rented. Use of immunoassay test kits is consistent with 29 CFR 1910.120(o),
which contains HAZWOPER requirements for the introduction of effective new technologies
and equipment for improved employee protection.
The following companies produce immunoassay kits that might be adaptable for surface
contamination sampling: EM Science (800-222-0342), Ensys Inc. (919-941-5509), Millipore
(800-225-1380), and Ohmicron (800-544-8881). For other potential sources of these kits,
check with your sampling equipment supplier.
Superfund site audits conducted from 1992 to 1995 by the EPA/Labor Superfund Health and
Safety Task Force led to the development of this article. Information about common safety
and health deficiencies observed by the audit team is available in a report titled
"Summary
Report on OSHA Inspections Conducted at Superfund Incinerator Sites." Copies of this report can be obtained
from the OSHA Publications Office, U.S. Department of Labor, P.O. Box 37535, Washington,
D.C. 20013-7535, or by calling 202-219-4667 or faxing to 202-219-9266.
Is Worker PPE Performing As Anticipated?
If dermal absorption or contamination is a potential hazard on your site, the
effectiveness of site PPE in preventing dermal exposure should be evaluated.
As workers exit the exclusion zone, the inner surfaces of their gloves and the sleeves
or collar of their PPE can be sampled to detect permeation of contaminants. In some
instances, the workers' skin can be sampled directly, although caution is necessary in
using this technique. Direct skin sampling should not be done for substances that are
irritants, cause dermatitis or contact sensitization, are easily absorbed by the skin, or
are corrosive.
Skin, PPE, or surfaces that contact food or tobacco should be analyzed using the item
wash method or should be wiped with a filter that is dry or wetted only with distilled
water, not with organic solvents, PPE that is decontaminated and reused on site should
occasionally be reevaluated, since chemical permeation may occur over time.
For some types of contaminants, colorimetric patches that adhere to the skin or to
inner layers of gloves or clothing are available. These patches change color when chemical
breakthrough occurs. Contact your sampling equipment supplier or the OSHA Salt Lake
Technical Center Analytical Laboratory (801-487-0680) for more information about PPE
sampling methods.
Guidance from OSHA's Technical Manual:
Standard Wipe Sampling Techniques
For Standard wipe sampling, a glass filter or a paper filter is generally used for a
sample collection. Through a template with an opening of known size (100 cm2is
standard), the surface to be sampled is "wiped" with the filter paper, using
maximum pressure and moving in concentric squares from the outside to the inside of the
sampling area. The filter is then folded with the exposed side in, placed in a sampling
vial, and sent to a laboratory for analysis.
The type of filter chosen depends on the contaminant and the analytical method used in
the laboratory, OSHA's Chemical Information Manual or your analytical laboratory can
provide chemical-specific guidance about wipe sampling methods.
General guidelines for surface contamination sampling include the following:
- Wear clean gloves for each sample.
- Use gloves that are disposable, impervious, and non-powdered.
- Do not take direct skin wipes for materials with high skin absorption. Instead, sample
surfaces that might contact the skin, such as the inside surfaces of protective gear or
the outside surfaces of equipment, tools, tabletops, and the like.
Alternatively, rinse the skin with water and analyze the rinse water (i.e., item wash method; see "Is
Worker PPE Performing As Anticipated?" page 50, for more information about evaluating
contamination on the skin's surface).
- consider wetting the sampling filter with distilled water or other solvent to improve
collection. The moistening agent can help dissolve the contaminant being sampled and
should be chosen accordingly. For example, collection of materials with low solubility,
such as PNAs or naphthalene, would be hampered by using water as a moistening agent,
whereas toluene or xylene might improve collection.
- Do not use organic solvents as a moistening agent when sampling surfaces that contact
the skin, food, or tobacco products. Use distilled or deionized water as a moistening
agent or a dry filter, or use the item wash method described above. Due to their volatile
nature, most organic solvents are not suitable for wipe sampling.
1Inspections shall be conducted by the site safety and
health supervisor or , in the absence of that individual, another individual who is
knowledgeable in occupational safety and health, acting on behalf of the employer as
necessary to determine the effectiveness of the site safety and health plan. Any
deficiencies in the effectiveness of the site safety and health plan shall be corrected by
the employer.
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