SECTION II: CHAPTER 2 [Extensively Revised and Featuring New Additions]
SAMPLING FOR SURFACE CONTAMINATION
Contents:
- INTRODUCTION.
- Worksite analysis (i.e., hazard assessment) is a basic component of an effective safety and health program. A complete worksite analysis requires the assessment of surface contamination since workers may be exposed to
these contaminants directly through dermal and ingestive routes (e.g., isocyanates, pesticides), and indirectly through inhalation of contaminants that become re-entrained in the air (e.g., asbestos, lead).
- Dermal and ingestive routes of entry are much more significant than inhalation for a large number of chemicals. For example, a fifteen-minute exposure of the hands and forearms to liquid glycol ethers [2-methoxy-ethanol
(ME) and 2-ethoxy-ethanol (EE)] will result in a dose to the body well in excess of the eight-hour inhalation dose at their recommended air exposure limits. (Biological monitoring for the urinary
metabolites methoxyacetic acid and ethoxyacetic acid was used to estimate the absorption via skin and lung.) Unfortunately, many industrial hygienists are only familiar with air sampling and fail to evaluate significant
exposures caused by surface contamination.
- Wipe sampling is an important tool of worksite analysis for both identifying hazardous conditions, and in evaluating the effectiveness of personal protective equipment, housekeeping, and decontamination programs. As
described below, wipe sampling is an important tool for assessing compliance with certain OSHA requirements even though there are few specific criteria for acceptable surface contamination amounts.
- The terms wipe sampling, swipe sampling, and smear sampling are synonyms that describe the techniques used to assess surface contamination on the skin, work surfaces, and PPE surfaces (e.g., gloves, respirators, aprons,
etc.) The term "wipe sampling" will be used in this document.
- THE USE OF SURFACE CONTAMINATION SAMPLING IN EVALUATING SAFETY AND HEALTH PROGRAMS.
29 CFR 1910.132 requires employers to "assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the
use of personal protective equipment (PPE)." To this purpose, wipe sampling can be useful in categorizing work areas for certain types of controls, such as PPE and/or special cleaning and decontamination. It is also useful in
assessing the effectiveness of these controls, including proper work practices. Examples are provided below for three generalized work areas: controlled areas that require the use of PPE, controlled areas that require the use
of special cleaning and/or decontamination, and non-controlled work areas that require neither PPE or special cleaning.
- CONTROLLED WORK AREAS REQUIRING PPE.
- These are areas where it has been determined (e.g., from an employer's hazard assessment) that PPE is necessary to prevent dermal exposures to a surface contaminant in spite of an aggressive, yet feasible cleaning
regimen. Many production areas and specific job tasks fall into this category.
- Wipe sampling can be used in assessing the effectiveness of the PPE program. Many elements of PPE programs are intended to prevent contamination to certain locations, such as the use of gloves to prevent contamination
to the skin of the hands. Surface contamination found in those "protected" locations usually indicates a problem with the program. For example, the presence of surface contamination inside a glove is normally the
result of either PPE failure (e.g., the contaminate soaked through the glove material or a tear in the glove), and/or an improper work practice for using the PPE, such as the worker inserting a contaminated hand
inside the glove. Additional sampling and observation can be used to determine the specific source of the program failure and possible abatement (e.g., changing gloves more often, checking for tears before donning,
cleaning hands before donning, etc.). Sampling after abatement measures are implemented can be used to show the effectiveness of the abatement.
- It is important to recognize that this sampling is not attempting to assess the health risk resulting from the contamination inside the glove. Rather, it is to identify failures in the PPE program. Therefore, the
criteria for concluding that contamination exists does not need to be quantitative. Criteria and reproducible procedures should be selected that provide confidence that contamination has not been adequately controlled
(i.e., contaminant levels are above background). The use of wipe pads that change color upon contact with the contaminant is ideal both in locating contamination and as a visual tool in training workers on the consequences
of poor work practices.
- CONTROLLED WORK AREAS REQUIRING SPECIAL CLEANING.
- Wipe sampling in these areas can show that a feasible and practical regimen of special cleaning and/or decontamination precludes the need for PPE or additional cleaning. The cleaning of lunch room tables, and the
decontamination of equipment before being removed from a restricted area are examples of this category. Other examples include cleaning surfaces to reduce accumulation of toxic materials (e.g., asbestos, lead, beryllium)
that may become re-suspended in air and thus contribute to airborne exposures.
- Wipe sampling is used in these areas as a quality control test of the specialized cleaning (or decontamination) regimen. Therefore, samples are taken to assess contamination levels of those surfaces for which the
special cleaning is required. Samples found in excess of an acceptable, task-specific, surface contamination limit (see below) indicate a failure in the cleaning or decontamination program. More aggressive
training and supervision of the cleaning procedures and/or scheduling may need to be implemented.
- Again, it is important to recognize that this sampling is not attempting to assess the health risk resulting from the contamination. Rather, it is to ensure that the cleaning and decontamination regimen is being
effectively implemented. Establishing an acceptable contamination limit will depend on the purpose of the cleaning, and what is feasible for the procedures utilized. For example, periodic vacuuming of floor surfaces
in a lead production area may be used to reduce the amount of lead dust available for re-entrainment, but significant lead contamination of the floor would still be expected. An acceptable surface contamination
limit for this type of cleaning would be set much higher than a limit used to evaluate cleaning of tables in the break room.
- A few surface contamination concentration guidelines have been published, but typically concentration limits must be established by an employer for a specific task. The limits should be based on sufficient initial
sampling to determine a "normal" range of contamination that can be expected after utilizing prescribed cleaning procedures. It would be appropriate to include documentation for the limits and their purpose, in the
worksite Safety and Health Program.
- NON-CONTROLLED WORK AREAS.
- These are work areas for which no special cleaning or PPE are required by the Safety and Health Program. Examples of this category are office areas that are physically separated from the production areas. These areas
are often "assumed" to have no significant contamination. Wipe sampling is useful in demonstrating the lack of contamination. If samples do show contamination, further investigation would be needed to determine the
cause. Consistent positive results would require a re-assessment of whether the area requires controls.
- As with sampling to evaluate PPE programs described above, procedures and criteria for sampling non-controlled areas need to provide confidence that contamination has not occurred (i.e., surface
concentrations are not above background). Again, the use of wipe pads which change color upon contact with the contaminant is ideal. The "direct reading" capability makes it possible to quickly screen an entire work
area (and a single pad may be used for multiple locations within the area).
- Sample those locations within the non-controlled area that accumulate dust (e.g., tops of filing cabinets), and surfaces that have potential for contamination from production areas (e.g., paper work brought in from
the production areas).
- Additional surfaces to consider for sampling include those that may come into contact with food and other materials that are ingested or placed in the mouth (e.g., chewing tobacco, gum, cigarettes).
Contaminated smoking materials may allow toxic materials or their combustion products (e.g., lead, mercury) to enter the body via the lungs. Wiping of surfaces that smoking materials may touch, including the hands, may
be useful in evaluating this possible route of exposure.
- EVALUATION OF SAMPLING RESULTS.
- The investigator must use professional judgment on a case-by-case basis when evaluating the significance of wipe-sampling results. As described above, acceptable surface contamination amounts
will vary widely for the same toxic agent depending on the purpose and location of the sample. Any concentration above background is sufficient to identify a problem with the PPE program for some sample locations.
- When evaluating results, consider the toxicity and the contribution of skin absorption and/or gastrointestinal absorption to the total dose. Additional factors are the ambient-air concentrations, skin
irritation, etc.
- The OSHA Technical Links Internet site includes Chemical Sampling Information which lists substances that have a potential for ingestion toxicity, skin absorption, and/or a hazardous effect on skin. This information may be found under
the "Health Factors" notation. Additional toxicological information concerning chronic skin absorption, dermatitis, etc. should be used in determining if the resulting
exposure presents a potential employee hazard (see Bibliography and other references in Technical Links).
- MEDIA AND TECHNIQUES FOR WIPE SAMPLING.
- SAMPLING SURFACES FOR CONTAMINATION.
- Techniques and media for collection of wipe samples from surfaces vary with the agent and purpose of the sample. It is recommended that the Technical Links Chemical Sampling Information, and/or the Salt Lake Technical Center's Applied Industrial Hygiene and Chemical Procedures Group be consulted when selecting a sampling procedure for a specific
chemical or contaminant.
- Classic wipe sampling techniques involve wiping a surface with a filter, which is then submitted to the SLTC for chemical analysis.
a. Glass fiber filters (GFF), 37 mm in diameter as used in air sampling, are recommended for many chemicals that are analyzed by gas chromatography (GC), or high-performance liquid chromatography (HPLC).
These may be used dry, or wetted with an appropriate solvent as specified in the Technical Links Chemical Sampling Information file.
b. Paper filters are generally used for collection of metals. Mixed cellulose ester filter discs (AA filters) or smear tabs, or their equivalent, are most often recommended.
c. Polyvinyl chloride filters are available for substances which are unstable on paper-type filters.
d. Squares of a gauze material, available from the Salt Lake Technical Center upon request, may be used for many organic substances, and have the advantage of being more durable than filter media, especially when
wiping rough surfaces. They may be used dry, or wetted with water or solvent to enhance collection efficiency.
e. Charcoal-impregnated pads may be useful for collection of volatile solvents from surfaces. They work by trapping the solvent on activated charcoal, similar to air sampling charcoal tubes.
f. In certain specialized cases, such as isocyanates and aromatic amines, highly reactive and unstable compounds must be collected on a filter medium that has been treated with a derivatizing reagent. These are
available from the SLTC quality control department.
- For a limited number of chemicals, direct-reading colorimetric wipe sampling procedures are available for qualitative or semi-quantitative detection of surface contaminants. These can be
used for acids and bases, isocyanates, aromatic amines, organic solvents (not solvent specific), lead, platinum salts, explosives and hydrazine. Contact the Salt Lake Technical Center for more information.
- For a variety of pesticides and certain other toxic chemicals, immunoassay kits can provide qualitative or semi-quantitative information on-site, and within about an hour. Some wet chemistry
is required. Contact the Salt Lake Technical Center for more information.
- SAMPLING SKIN FOR CONTAMINATION.
- Techniques and media for wipe sampling of skin contamination vary with the agent and purpose of the sample. It is recommended that the Technical Links Chemical Sampling Information, and/or the Salt Lake Technical Center's Applied Industrial Hygiene and Chemical Procedures Group be consulted when selecting a sampling procedure for a specific
chemical or contaminant.
- There are concerns related to direct wipe sampling of the skin, including the possibility of promoting skin absorption with the use of certain solvents. Contact the Salt Lake Technical Center prior to taking wipe
samples directly on the skin to receive agent specific procedures and precautions. Where feasible, biological monitoring is often the most effective means of assessing overall absorption of a contaminant, including
through the skin.
- Before any skin wipe is taken, explain why you want the sample and ask the employee about possible skin allergies to the chemicals in the sampling medium or wetting solution. Employees may elect not to allow sampling
of their skin.
- As an alternative to direct skin sampling, an indirect measurement of skin contamination (as well as PPE failure) can be assessed by wipe sampling surfaces that workers can touch (e.g., table tops, handles, control
knobs, inside surfaces of protective equipment).
- Classic wipe sampling techniques as described earlier, employing glassfiber filters, mixed cellulose ester filters or smear tabs, or gauze squares, charcoal impregnated pads, may be used for sampling contaminants
on the skin. If it is deemed desirable to moisten the collecting medium to improve collection efficiency, procedures will normally utilize distilled or de-ionized water, or a 50% solution of isopropyl
alcohol in water.
- Hand washes may be appropriate in some cases. Twenty ml of distilled or de-ionized water, or a dilute solution of mild soap may be added to a zipper-style sandwich bag. The hand to be sampled
is inserted, and the bag held tightly closed around the wrist. After a few seconds of agitation, the hand is carefully removed, and the wash solution is poured back into a scintillation vial for shipment to the laboratory.
- For a limited number of chemicals, direct-reading colorimetric wipe sampling procedures are available for qualitative or semi-quantitative detection of contaminants. These can be used for
acids and bases, isocyanates, aromatic amines, organic solvents (not solvent-specific), platinum salts, and hydrazine. The technique differs from that used for surface wipes. Contact the Salt Lake Technical
Center for more information.
- The same technology employed in the colorimetric wipe sampling procedures described above has been applied to a band-aid-type format. These can be applied to the hands inside gloves to demonstrate glove
permeability or breakthrough. They can serve as an excellent tool in employee training.
- PROCEDURES FOR COLLECTING WIPE SAMPLES.
- Preloading a group of vials with appropriate filters is a convenient method to carry the sample media to the worksite. (The smear tabs should be inserted with the tab end out.) Clean plastic gloves should be worn
when handling the filters. The gloves should not be powdered.
- The following are general procedures for taking wipe samples:
a. If multiple samples are to be taken at the worksite, prepare a rough sketch of the area to be wipe sampled.
b. A new set of clean, impervious gloves should be used for each sample to avoid contamination of the filter by previous samples (and the possibility of false positives) and to prevent contact with the substance.
c. Withdraw the filter from the vial with your fingers or clean tweezers. If a damp wipe sample is desired, moisten the filter with distilled water or other solvent as recommended.
d. Depending on the purpose of the sample, it may be useful to determine the concentration of contamination (e.g., in micrograms of agent per area). For these samples, it is necessary to record the area of the
surface wiped (e.g., 100 cm2). This would normally not be necessary for samples taken to simply show the presence of the contaminant.
e. Firm pressure should be applied when wiping.
f. Start at the outside edge and progress toward the center of the surface area by wiping in concentric squares of decreasing size.
g. Without allowing the filter to come into contact with any other surface, fold the filter with the exposed side in. If possible, use the same filter to repeat the sampling of the same area, then fold it over
again. Place the filter in a sample vial, cap and number it, and note the number at the sample location on the sketch. Include notes with the sketch giving any further description of the sample (e.g., "Fred Employee's
respirator, inside"; "Lunch table").
h. At least one blank filter treated in the same fashion, but without wiping, should be submitted for each sampled area.
i. Some substances should have solvent added to the vial as soon as the wipe sample is placed in the vial (e.g., benzidine). These substances are indicated with an "X" next to the solvent notation in the Technical
Links Chemical Sampling Information File.
j. Submit the samples to the Salt Lake Technical Center (SLTC) with an OSHA 91 form.
- BIBLIOGRAPHY.
Adams, R.M. 1983. Occupational Skin Disease. New York: Grune and Stratton.
Benezra, C. et al. 1982. Occupational Contact Dermatitis. Clinical and Chemical Aspect. Philadelphia; Saunders. 1st ed.
Chaiyuth, C. and L. Levin. "A laboratory evaluation of wipe testing base on lead oxide surface contamination." Am. Ind. Hyg. Assoc. J. 45:311-317, 1984.
Clayton, G.D. and F.E. Clayton. 1981. Patty's Industrial Hygiene and Toxicology. New York: John Wiley and Sons. Vol. II.
Fisher, A.A. 1986. Contact Dermatitis. Philadelphia: Lea and Febriger. 3rd ed.
Gellin, G. and H.I. Malbach. 1982. Occupational and Industrial Dermatology. Chicago: Year Book Medical Publisher.
Lees, P.S.J. et al. "Evidence for dermal absorption as the major route of body entry during exposure of transformer maintenance and repairman to PCBs." Am. Ind. Hyg Assoc. J. 48:257-264, 1987.
Occupational Safety and Health Administration (OSHA), U.S. Dept. of Labor. 1995. "Chemical Sampling Information." Washington, D.C. Available on the OSHA Internet site.
Kezic, Sanja; et al.; Dermal absorption of vaporous and liquid 2-methoxyethanol and 2-ethoxyethanol in volunteers, Occup. Environ. Med., 54, 1997, pp. 38-43.
APPENDIX II:2-1. SUBSTANCES LISTED WITH A SKIN NOTATION BY THE ACGIH TLV's AND/OR THE OSHA PEL's
NAME:
|
CAS # :
|
| B) Acrylamide |
79-06-1 |
| T) Acrylic acid |
79-10-7 |
| T) Acrylonitrile |
107-13-1 |
| B) Aldrin |
309-00-2 |
| B) Allyl Alcohol |
107-18-6 |
| T) 4-Aminodiphenyl |
92-67-1 |
| B) Aniline |
62-53-3 |
| B) Anisidine (o,p-Isomers) |
29191-52-4 |
| B) Azinphos-Methyl |
86-50-0 |
| T) Benzidine |
92-87-5 |
| B) Bromoform |
75-25-2 |
| B) 2-Butoxyethanol |
111-76-2 |
| T) n-Butyl Alcohol |
71-36-3 |
| B) Butylamine |
109-73-9 |
| B) tert-Butyl Chromate (as CrO3) |
1189-85-1 |
| T) o-sec-Butylphenol |
89-72-5 |
| T) Captafol |
2425-06-1 |
| T) Carbon Disulfide |
75-15-0 |
| T) Carbon Tetrachloride |
56-23-5 |
| T) Catechol |
120-80-9 |
| B) Chlordane |
57-74-9 |
| B) Chlorinated Camphene |
8001-35-2 |
| T) Chloroacetyl Chloride |
79-04-9 |
| T) o-Chlorobenzylidene |
2698-41-1 |
| T) Malononitrile |
|
| B) Chlorodiphenyl (42% Cl) |
53469-21-9 |
| B) Chlorodiphenyl (54% Cl) |
11097-69-1 |
| B) Chloroprene |
126-99-8 |
| T) Chlorpyrifos |
2921-88-2 |
| B) Cresol (All Isomers) |
1319-77-3 |
| B) Cumene |
98-82-8 |
| B) Cyanide (as Cn) |
57-12-5 |
| T) Cyclohexanol |
108-93-0 |
| T) Cyclohexanone |
108-94-1 |
| T) Cyclonite |
121-82-4 |
| P) DDT |
50-29-3 |
| B) Decaborane |
17702-41-9 |
| B) Demeton |
8065-48-3 |
| T) Diazinon |
333-41-5 |
| T) 2-n-Dibutylaminoethanol |
102-81-8 |
| T) 3,3'-Dichlorobenzidine |
91-94-1 |
| B) Dichloroethyl Ether |
111-44-4 |
| T) 1,3-Dichloropropene |
542-75-6 |
| B) Dichlorvos (DDVP) |
62-73-7 |
| T) Dicrotophos |
141-66-2 |
| B) Dieldrin |
60-57-1 |
| T) Diethanolamine |
111-42-2 |
| T) Diethylamine |
109-89-7 |
| B) Diethylamino ethanol |
100-37-8 |
| T) Diethylenetriamine |
111-40-0 |
| B) Diisopropylamine |
108-18-9 |
| B) Dimethyl Acetamide |
127-19-5 |
B) Dimethylaniline
(N,N-Dimethylaniline) |
121-69-7 |
T) Dimethyl-1,2-dibromo-2,
2-dichloroethyl phosphate |
300-76-5 |
| B) Dimethylformamide |
68-12-2 |
| B) 1,l-Dimethylhydrazine |
57-14-7 |
| B) Dimethyl Sulfate |
77-78-1 |
| B) Dinitrobenzene (All isomers) |
25154-54-5 |
| B) Dinitro-o-cresol |
534-52-1 |
| B) Dinitrotoluene |
25321-14-6 |
| B) Dioxane |
123-91-1 |
| T) Dioxathion |
78-34-2 |
B) Dipropylene Glycol
Methyl Ether |
34590-94-8 |
| T) Diquat |
85-00-7 |
| T) Disulfoton |
298-04-4 |
| B) EPN |
2104-64-5 |
| T) Endosulfan |
115-29-7 |
| B) Endrin |
72-20-8 |
| B) Epichlorohydrin |
106-89-8 |
| T) Ethion |
563-12-2 |
| B) 2-Ethoxyethanol |
110-80-5 |
| B) 2-Ethoxyethyl Acetate |
111-15-9 |
| P) Ethyl Acrylate |
140-88-5 |
| T) Ethylamine |
75-04-7 |
| T) Ethyl Bromide |
74-96-4 |
| B) Ethylene Chlorohydrin |
107-07-3 |
| T) Ethylenediamine |
107-15-3 |
| T) Ethylene Dibromide |
106-93-4 |
| B) Ethylene Glycol Dinitrate |
628-96-6 |
| B) Ethyleneimine |
151-56-4 |
| B) N-Ethylmorpholine |
100-74-3 |
| T) Fenamiphos |
22224-92-6 |
| T) Fenthion |
55-38-9 |
| T) Fonofos |
944-22-9 |
| T) Formamide |
75-12-7 |
| T) Heptachlor |
76-44-8 |
| T) Hexachlorobenzene |
118-74-1 |
| T) Hexachlorobutadiene |
87-68-3 |
|
NAME:
|
CAS # :
|
| T) Hexachloroethane |
67-72-1 |
| B) Hexachloronaphthalene |
1335-87-1 |
| T) Hexafluoroacetone |
684-16-2 |
| T) Hexamethyl phosphoramide |
680-31-9 |
| T) 2-Hexanone |
591-78-6 |
| B) Hydrazine |
302-01-2 |
| B) Hydrogen Cyanide |
74-90-8 |
| B) Lindane |
58-89-9 |
| B) Malathion (Total Dust) |
121-75-5 |
T) Manganese Cyclopentadienyl
Tricarbonyl (as Mn) |
12079-65-1 |
T) Mercury (organo) Alkyl
Compounds (as Hg) |
|
| T) Mercury (Vapor) (as Hg) |
7439-97-6 |
| B) Methyl Acrylate |
96-33-3 |
| T) Methyl Acrylonitrile |
126-98-7 |
| T) Methyl Alcohol |
67-56-1 |
| B) Methyl Bromide |
74-83-9 |
| B) Methyl Cellosolve |
109-86-4 |
| B) Methyl Cellosolve Acetate |
110-49-6 |
| T) Methyl Chloride |
74-87-3 |
| T) o-Methylcyclohexanone |
583-60-8 |
| T) Methylcyclopentadienyl |
12108-13-3 |
| T) Methyl Demeton |
8022-00-2 |
T) 4,4'-Methylene-bis
(2-Chloroaniline) |
101-14-4 |
| T) 4,4'-Methylenedianiline |
101-77-9 |
| B) Methyl Iodide |
74-88-4 |
| B) Methyl Isobutyl Carbinol |
108-11-2 |
| B) Methyl Isocyanate |
624-83-9 |
| T) Methyl Parathion |
298-00-0 |
| T) Monocrotophos |
6923-22-4 |
| T) Monomethyl Aniline |
100-61-8 |
| B) Monomethyl Hydrazine |
60-34-4 |
| B) Morpholine |
110-91-8 |
| B) Nicotine |
54-11-5 |
| B) p-Nitroaniline |
100-01-6 |
| B) Nitrobenzene |
98-95-3 |
| T) 4-Nitrodiphenyl |
92-93-3 |
| B) p-Nitrochlorobenzene |
100-00-5 |
| B) Nitroglycerin |
55-63-0 |
| T) N-Nitrosodimethylamine |
62-75-9 |
| B) Nitrotoluene |
99-08-1 |
| B) Octachloronaphthalene |
2234-13-1 |
| P) Paraquat, respirable dust |
1910-42-5 |
| B) Parathion |
56-38-2 |
| T) Pentachloronaphthalene |
1321-64-8 |
| B) Pentachlorophenol |
87-86-5 |
| B) Phenol |
108-95-2 |
| T) Phenothiazine |
92-84-2 |
| P) p-Phenylene Diamine |
106-50-3 |
| T) Phenyl Glycidyl Ether |
122-60-1 |
| B) Phenylhydrazine |
100-63-0 |
| T) Phorate |
298-02-2 |
| B) Phosdrin |
7786-34-7 |
| P) Picric Acid |
88-89-1 |
| T) Propargyl Alcohol |
107-19-7 |
| T) Propyl Alcohol |
71-23-8 |
| T) 1,2-Propylene Glycol Dinitrate |
6423-43-4 |
| B) Propylene Imine |
75-55-8 |
| B) Sodium Fluoroacetate |
62-74-8 |
| T) Styrene |
100-42-5 |
| B) TEDP |
3689-24-5 |
| B) TEPP |
107-49-3 |
| T) 1,1,2,2-Tetrachloroethane |
79-34-5 |
| P) Tetrachloronaphthalene |
1335-88-2 |
| B) Tetraethyl Lead (as Pb) |
78-00-2 |
| B) Tetramethyl Lead (as Pb) |
75-74-1 |
| B) Tetramethyl Succinonitrile |
3333-52-6 |
| P) Tetryl |
479-45-8 |
| B) Thallium, soluble |
7440-28-0 |
| T) Thioglycolic Acid |
68-11-1 |
| T) Tin, organic compounds |
1983-10-4 |
| T) o-Tolidine |
119-93-7 |
| T) Toluene |
108-88-3 |
| T) m-Toluidine |
108-44-1 |
| B) o-Toluidine |
95-53-4 |
| T) p-Toluidine |
106-49-0 |
| T) 1,1,2-Trichloroethane |
79-00-5 |
| B) Trichloronaphthalene |
1321-65-9 |
| T) 1,2,3-Trichloropropane |
96-18-4 |
| T) Triethylamine |
121-44-8 |
| B) 2,4,6-Trinitrotoluene |
118-96-7 |
| T) Triorthocresyl Phosphate |
78-30-8 |
| T) Vinyl Cyclohexene Dioxide |
106-87-6 |
| T) m-Xylene-alpha,alpha'-diamine |
1477-55-0 |
| T) Xylidine |
1300-73-8 |
| Note: |
P = Skin notation in the PEL
T = Skin notation in the TLV
B = Skin notation in both references |
|
APPENDIX II:2-2. EXAMPLE PROCEDURES FOR ISOCYANATES
This example is provided for information only and should not be taken as the basis for OSHA policy.
| Prepared by: Richard Lawrence, Chemist |
Date: August 21, 1997 |
Aromatic Isocyanate Surface Contamination Sampling and Evaluation Techniques
The OSHA Salt Lake Technical Center received a request for assistance at a facility that uses methylene bisphenyl isocyanate (MDI, CAS no. 101-68-8) in their production process. It was decided that an inspection would include screening
and sampling for possible MDI surface contamination (as well as air sampling for MDI). The following surface monitoring techniques were evaluated in preparation for that inspection.
A route of workplace exposure to chemicals with low vapor pressures, such as aromatic isocyanates, may be through skin contact with contaminated solvents or surfaces (1,2). Aromatic isocyanates present a respiratory sensitization
hazard (1,2). Laboratory studies with animals have indicated that respiratory sensitization to both TDI (3,4) and MDI (5) can be induced by dermal contact alone. The ability to determine surface contamination may be useful in evaluating
the effectiveness of housekeeping, decontamination and chemical protective equipment.
Direct reading indicators, such as commercially prepared pads that change color when they come in contact with specific chemicals (or classes of chemicals), are available for aromatic isocyanates. These types of indicators may be
used as a screening tool, when assessing the extent of surface contamination, because they are inexpensive and the results are immediate. If an indicator wipe yields a positive result, a wipe sample can then be taken and sent to
a laboratory for confirmation.
The mention of the commercial products Swypes® and Permea-Tec® does not constitute an endorsement but is inteded solely as an identification of the type of product deemed suitable for the use intended.
The use of direct reading instruments and indicators can be effective in helping employers to comply with the OSHA personal protective equipment standard, 29 CFR 1910.132 (d)(1)(I) and (f)(1)(iii) and (iv). Wipe Sampling for Screening
| Materials: |
At the time of the inspection, the OSHA Salt Lake Technical Center had an aromatic isocyanate indicator wipe kit in stock called a Swype® kit (6). This kit consists of indicator wipes called Swype®,
a spray bottle of a developer solution that contains a chemical which activates the Swype®, and indicator patches that are worn under PPE, such as gloves, to test the effectiveness. The kit also contains
a spray bottle of decontamination solution and a skin cleaner. The effectiveness of the skin cleaner and decontamination solution was not investigated.
1. Gloves and other personal protective equipment must be worn during testing, as appropriate. "Best" style 727 nitrile gloves should provide protection to the hygienist's hands for the time required to perform the screening.
2. Gloves must be changed after a positive result to avoid cross contamination of any subsequent tests.
3. Spray the area to be sampled lightly with the Developer Solution. Use as little as needed to ensure that the surface is wet. Excess solution will dilute contamination, possibly below the detection limit. When testing
a vertical surface or knob, some of the solution may begin to "run-off" or drip. This "run-off" should be captured onto the pad to ensure that any contaminant present has not been lost. The
Developer Solution contains a proprietary component that activates the Swype® pad.
4. Wait approximately 30 seconds for any aromatic isocyanate to dissolve, then wipe the surface with a surface Swype® pad.
5. Allow 2 to 3 minutes for the color to develop. A pastel red-orange or pink color indicates aromatic isocyanate contamination. The color varies depending on the type of isocyanate present. The surface Swype®
detection limit is approximately 3-5 µg.
6. Record appropriate information as needed.
7. If the surface Swype® tests indicate a positive for contamination, the hygienist may want to take corresponding surface wipe samples for laboratory quantitation and confirmation in key samples. |
Wipe Sampling for Laboratory Analysis
| Materials: |
Glass fiber filters, scintillation vials and a derivatizing solution are required for this sampling procedure.
1. Gloves and other personal protective equipment must be worn during sampling, as appropriate. "Best" style 878 butyl gloves provide protection to the hygienist's hands for the time required to perform the sampling.
2. Gloves must be changed after obtaining each sample to avoid cross contamination of any subsequent samples.
3. A solution of 10.0 mg 1-(2-pyridyl) piperazine per milliliter acetonitrile is prepared. The 1-(2-pyridyl) piperazine is a derivatizing agent that stabilizes the isocyanate. The derivatives also allow
a greater sensitivity during the analysis.
4. Estimate the number of samples that will be taken. An overestimate might be better. Prepare vials by adding 1.0 milliliter of the 1-(2-pyridyl) piperazine solution to each vial. It is recommended that
the solution be pipetted into the vials in a controlled environment, before sampling, to eliminate any chance for contamination.
5. Untreated glass fiber filters are the appropriate wipe media.
6. Reagent grade acetonitrile is used to wet the filter. The acetonitrile acts as a solvent to dissolve and extract any contaminant present.
7. Using a dropper, wet the filter until almost dripping.
8. Select an area immediately adjacent to the area where the Swype® yielded a positive test result.
9. Using the filter, wipe an area about 100 cm2, rubbing the entire area side to side, then up and down. In many cases (such as knobs and levers) it may not be possible to wipe 100 cm2.
10. Place the filter in a scintillation vial containing the derivatizing solution, label the vial, and record appropriate information.
11. The samples are ready to be analyzed by a laboratory. The OSHA Salt Lake Technical Center uses OSHA method 47 for analysis of MDI, and OSHA method 42 for analysis of 2,6-TDI and 2,4-TDI.
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Monitoring Inside Protective Equipment (gloves, suits).
Studies have shown that solvents containing chemicals may act as a vehicle allowing the chemicals to permeate gloves and protective clothing (7). The Permea-Tec® aromatic isocyanates detection system
may be used for worksite evaluation of chemical protective PPE. For example, a negative result (no color change) of the Permea-Tec®, after being worn under a glove for a time period, in a work environment
known to have contaminants present, demonstrates that the glove protection was effective for that time period, in those working conditions. The Permea-Tec® is an indicating pad that is attached to a
band-aid-like adhesive strip.
1. Place one or more Permea-Tec® patches (pad side out) on the fingers, palms, wrist, lower arm (near cuff of glove), wherever there is likely to be permeation or contamination.
2. Workers should then don their PPE and work for a time period as they normally would. (If the workers normally change gloves every two hours, for example, then the time period is two hours.)
3. After the shift, allow the workers to doff the gloves as they normally would, then collect, identify, and note the color of the pads.
4. In most cases the Permea-Tec® pad should not need any further treatment. If solvent (containing isocyanates) permeation has occurred, then this solvent should be sufficient to activate the pad.
5. If permeation or penetration of the PPE by the solvent containing aromatic isocyanates has occurred, a reaction turns the pad a pastel red-orange to pink. It is a reliable indicator to a detection limit of 3-5
µg aromatic isocyanates.
Evaluating PPE for Dry Chemicals
1. There may be situations where the Industrial Hygienist may want to use Permea-Tec® pads for dry chemicals. (For example: unprotected handling of components that are assumed to be totally cured.) In
this case, after the pads have been collected, 3 drops of solvent (methanol works well) needs to be placed directly onto the pad. Again gloves must be worn during sampling and solvent dispensing.
2. The methanol (or other solvent) wicks into the pad and enables a reaction that turns the pad a pastel red-orange to pink if aromatic isocyanate contamination is present. It is a reliable indicator to a detection
limit of 3-5 µg.
References
1. "Preventing Asthma and Death from Diisocyanate Exposure", Department of Health, Education and Welfare, NIOSH, ALERT, Cincinnati, OH, March, 1996, DHHS (NIOSH) Publication No. 96-111, 2-3.
2. Material Safety Data Sheet for MDI, DOW Chemical Company, Midland, MI, 1995, MSD002334, 1.
3. Bickis, U. Investigation of dermally induced airway hyperreactivity to toluene diisocyanate in guinea pigs. Ph.D. thesis, Department of Pharmacology and Toxicology, Queen's University, Kingston, Canada. November, 1994.
4. Karol, M.H., Hauth, B.A., Riley, E.J., and Magreni, C.M. Dermal contact with toluene diisocyanate (TDI) produced respiratory tract hypersensitivity in guinea pigs. Toxicol. Appl. Pharmacol, 1981, 58, 221-230.
5. Rattray, N.J., Botham, P.A., Hext, P.M., Woodcock, D.R., Fielding, I., Dearman, R.J., and Kimber, I. Induction of respiratory hypersensitivity to diphenylmethane-4,4'-diisocyanate (MDI) in guinea pigs. Influence
of route of exposure. Toxicology, 1994, 88, 15-30.
6. CLI, Colormetric Laboratories, Inc. 1261A Rand Road, Des Plaines, IL, 60016-3402, Telephone: (847) 696-3036.
7. Gunderson, E. C., Kingsley, B. A., Witham,C. L. and Bromberg, D.C. A Practical Study in Laboratory and Workplace Permeation Testing. Appl. Ind. Hyg., 1989, Vol. 4, 12, 324-329.
APPENDIX II:2-3. EXAMPLE PROCEDURES FOR AROMATIC AMINES
This example is provided for information only and should not be taken as a basis for OSHA policy.
| Prepared by: Richard Lawrence, Chemist |
Date: August 21, 1997 |
Aromatic Amine Surface Contamination Sampling and Evaluation Techniques
Air sampling by itself may be an inadequate technique to evaluate potential worker exposure to compounds with a low vapor pressure, such as aromatic amines (e.g., MOCA, MDA). A major route of workplace exposure to these chemicals
is through skin contact with contaminated surfaces. Aromatic amines are persistent chemicals and once released into the work environment they may remain on surfaces for months and even years. When contaminated surfaces are contacted
by unprotected skin, significant exposures are possible. This screening and sampling technique can be useful in evaluating the effectiveness of chemical protective equipment, housekeeping, and decontamination.
Direct reading indicators, such as commercially prepared pads that change color when they come in contact with specific chemicals (or classes of chemicals), are available for aromatic amines. These types of indicators may be used
as a screening tool, when assessing the extent of surface contamination, because they are inexpensive and the results are immediate. If an indicator wipe yields a positive result, a wipe sample can then be taken and sent to a laboratory
for confirmation.
The mention of the commercial products Swypes® and Permea-Tec® does not constitute an endorsement but is intended solely as an identification of the type of product deemed suitable for the use intended.
The use of direct reading instruments and indicators can be effective in helping employers to comply with the OSHA personal protective equipment standard, 29 CFR 1910.132 (d)(1)(I) and (f)(1)(iii) and (iv).
-Using the surface contamination Swype®*.
1. Gloves and other personal protective equipment must be worn during testing, as appropriate.
2. Gloves must be changed after a positive result to avoid cross contamination of any subsequent tests.
3. Spray the area to be sampled lightly with the Cleaning Solution. Use as little as needed to ensure that the surface is wet. Excess solution may dilute any contamination, possibly to less than the detection limit. When testing
a vertical surface or knob, some of the solution may begin to "run-off" or drip. This "run-off" should be captured onto the pad to ensure that any contaminant present has not been lost. The Cleaning Solution
contains a proprietary component which activates the Swype® pad.
4. Wait approximately 30 seconds for any aromatic amine to dissolve, than wipe the surface with a surface Swype® pad.
5. Allow 2 to 3 minutes for the color to develop. A red color indicates aromatic amine contamination. The surface Swype® detection limit is approximately 3-5 µg.
6. Record appropriate information as needed.
7. If the surface Swype® tests indicate a positive for contamination, the hygienist may want to take corresponding surface wipe samples for laboratory quantitation. The laboratory may also confirm the presence of
the contaminant in key samples.
-Taking a surface wipe sample.
1. Gloves and other personal protective equipment must be worn during sampling, as appropriate.
2. Gloves must be changed after obtaining each sample to avoid cross contamination of any subsequent samples.
3. Glass fiber filters that have been prepared for air sampling for MOCA or MDA are the appropriate wipe media. These filters have been prepared by soaking each filter with 0.5 ml of 0.26 N sulfuric acid and drying them in an oven.
The sulfuric acid converts the amine to a more stable amine salt.
4. A solution of 60/40 v/v methanol/water is used to wet the filter. The methanol acts as a solvent to dissolve and extract any contaminant present. The water activates the sulfuric acid already in the filter.
5. Using a dropper, wet the filter until it is almost dripping.
6. Select an area immediately adjacent to the one where the Swype® yielded a positive test result.
7. Using the filter, wipe an area about 100 cm2, rubbing the entire area from side to side, then up and down. In many cases, such as knobs and levers, it may not be possible to wipe 100 cm2.
8. Place the filter in a scintillation vial, label the vial, and record appropriate information.
9. The samples are ready to be analyzed by a laboratory. The OSHA Salt Lake Technical Center uses OSHA method 71 for analysis of MOCA, and OSHA method 57 for analysis of MDA.
-Monitoring Inside Protective Equipment (gloves, suits).
Field and laboratory studies have shown that aromatic amines may permeate gloves and protective clothing. The Permea-Tec® aromatic amine detection system may be used for work site evaluation of chemical protective
PPE. For example, a negative result (no color change) of the Permea-Tec®, after being worn under a glove for a time period, in a work environment known to have contaminants present, demonstrates that the glove protection
was effective for that time period, in those working conditions. The Permea-Tec® is an indicating pad similar to the Swype® attached to a band-aid like adhesive strip.
1. Have the selected workers wear one or more Permea-Tec® patches (pad side out) on the fingers, palms, wrist, lower arm (near cuff of glove), wherever there is likely to be permeation or contamination.
2. After the shift, allow the workers to doff the gloves as they normally would, then collect, ID, and develop the pads.
3. To develop, ten drops of water are applied slowly to the white strip. The white strip contains a component that activates the Permea-Tec® pad.
4. The water wicks up into the pad and the pad turns red if aromatic amine contamination is present. It is a reliable indicator to a detection limit of 3-5 µg
The following compounds are among the suspected agents that can be detected through this procedure:
- methylene dianiline (MDA)
- 4,4'-methylene bis(2-chloroaniline)
- benzidine
- a-napthylamine
- b-napthylamine
- 4-aminobiphenyl
- o-toluidine
- aniline
- 2,4-toluenediamine
- 1,3-phenylenediamine
- napthylenediamine
- 2,4-xylidine
- o-chloroaniline
- 3,4-dichloroaniline
- r-nitroaniline
* Mention of the Swypes® and Permea-Tec® brand names does not constitute an endorsement of those products. (Back to text)
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