Health & Safety: Biological Monitoring in the Workplace

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This article originally appeared as a special Health & Safety Guide in AIC News--and may have been updated
Biological Monitoring in the Workplace
Date: November 1999
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This Page was Last Updated:November 1999

Clinic Listings

OSHA Respirator Medical Evaluation Questionnaire (Mandatory)

A Special Insert Contributed by the Health and Safety Committee

Conservators across all specialty groups work with a variety of potentially harmful chemical substances. They should be interested in knowing 1) what is their possible exposure risk, and 2) what adverse health effects, if any, have resulted from this exposure. The concept of conducting medical monitoring tests to identify signs or symptoms of disease is familiar to all physicians.

However, the goal of anyone working with hazardous materials is to prevent disease from even occurring. To do that, one needs first to establish whether your work materials or practices are resulting in measurable exposure to those hazards. The evaluation of health risk is a multi-faceted process best done by a specialist in the field of occupational hygiene or safety. The process, to be complete, should include repetitive sampling of the workplace ambient air to determine the anticipated inhalation exposure expected from a certain conservation task using particular chemicals. In addition, there are forms of biological monitoring which may be appropriate for a health professional to perform in the context of workplace risk evaluation. Your personal physicians can also conduct biological monitoring tests for occupational exposure, provided they are familiar with the standards specific to the specialized field of occupational medicine.

This Guide is intended to provide the conservator with useful references necessary to begin this process, by:

  • discussing how biological monitoring can be used by health professionals as a tool for assessing your exposure to chemicals in the workplace,
  • explaining the difference between biological (exposure) and medical (health effects) monitoring,
  • listing chemicals for which there are established guidelines or standards for biological monitoring, and
  • offering useful references and resources.

Explanation of terms

The health risk (or hazard) from a particular chemical is a function of both its toxicity and the exposure dose actually absorbed by the user.

  • Toxicity is the capacity of a material to produce injury or harm when the chemical has reached a sufficient concentration (dose) at a certain site in the body.
  • Exposure dose is the amount of chemical that has been absorbed by the body and could therefore reach that site to do harm.
  • The risk, or hazard, of working with that chemical is the probability that this dose concentration will occur.

In other words, a carcinogen used inside a properly functioning lab hood could pose far less of a health risk than a low-toxicity alcohol used in closed quarters, with poor ventilation and no skin protection.

Environmental monitoring can be used to determine exposure by looking at the concentration of the chemicals in the work environment. These tests would include airborne (inhalation exposure) samples and surface wipe samples. If the overall dose of a chemical enters the body through routes other than inhalation (i.e., ingestion or dermal) then biological monitoring of other media (like urine, exhaled breath, or blood) may be a better determinant of overall dose than air sampling alone. Biological monitoring also produces a pre-clinical measurement of the presence of the chemical, estimating the amount which has proceeded from the external to the internal environment. Finally, medical monitoring tests will be used by the physician to measure adverse health effect, or occupational illness, in a particular individual. By the time medical monitoring produces an indication of the chemical, the parameter measured is extent of biological effect, i.e., illness. Biological (exposure dose) monitoring and medical (health effect) monitoring, when assessed together, constitute a medical surveillance program, a term which usually applies to a study of health trends in a population of workers, not in an individual. This term is often used in the regulatory standards of the U.S. Occupational Safety and Health Administration (OSHA).

An Important Distinction to Understand

A primary distinction between biological and medical monitoring is that the former is an estimate of dose, the latter is a measure of the effect of that dose. In other words, for medical monitoring to produce an abnormal reading, the chemical must have already had an adverse effect on the person. Biological monitoring, on the other hand, can detect whether you have been measurably exposed to a chemical (hopefully before symptoms appear). For example, if conservators request periodic liver function tests because they are working with certain solvents, they will be waiting for a manifestation of the damage, rather than trying to determine if work exposures, as measured through air or exhaled breath samples, may be putting them at risk. Biological monitoring, if conducted according to validated occupational health protocols and within specified time frames, can serve as an invaluable red flag for conservators, particularly those who are working consistently with small amounts of highly hazardous chemicals, or have just been accidentally exposed to an atypically high concentration.

Routes of Exposure

Exposure to toxic substances in the workplace can result from chemicals being inhaled, ingested or being absorbed through the skin (including mucus membranes). Figure 1 presents the pathway by which a chemical substance in the workplace environment can produce toxic effect. By being aware of these routes of exposure, the conservator can both better judge the potential for exposure and also better control that exposure. For example, a large number of chemicals including some solids as well as many liquids, can be absorbed through intact skin and into the bloodstream. By being aware of this potential route of exposure, conservators can modify their work habits or even use protective clothing (e.g., impermeable gloves) to prevent this dermal absorption. Also, ingestion of a compound can be direct (e.g., hand to mouth) but is more likely to be indirect (e.g., substance getting onto food or drink in the workplace). The value of frequent washing and restrictions on consumption of food and beverage in the studio or lab should be obvious.

Environmental Monitoring

If inhalation is the only significant route of entry to the body, then the results of ambient air samples taken within the person's “breathing zone” reflect the dose of that chemical to the body. The collection device is placed close to the person's breathing zone, typically on the worker's lapel. The device may be connected to a battery-operated, calibrated sampling pump, which is worn through the work/exposure period, often an 8-hour shift or 15-minute short term exposure period. Validated sampling and analytical methods are followed, such as those published by the National Institute for Occupational Safety and Health (NIOSH). The sample is analyzed by a qualified laboratory for the concentration of the chemical studied, and the results are compared with established regulatory standards, such as the Permissible Exposure Limits (PELs) promulgated by the OSHA or consensus guidelines, such as the annually-revised Threshold Limit Values (TLVs) of the American Conference of Governmental Industrial Hygienists (ACGIH), or the NIOSH Recommended Exposure Limits (RELs). None of these concentrations should be construed as absolute lines between safe and unsafe exposures, but should be evaluated in the overall exposure assessment. Contacts for these organizations are listed in the reference section of this Guide.

Other techniques for estimating the potential for environmental exposures are occasionally used such as wipe samples to estimate the concentration of a toxic chemical on work surfaces or even on the workers skin. There are, however, only a few validated techniques for collecting and analyzing these types of samples, or standards against which to judge results (such as lead), so these procedures are generally of qualitative , not quantitative, value to the investigator.

Biological Monitoring

If significant exposure can occur through routes of entry other than inhalation, biological monitoring may be warranted. The most widely accepted forms of biological monitoring include exhaled breath, urine, and blood testing. Alterations in these concentrations reflect absorption by all routes of entry, reflect physiological responses unique to the individual, and offer information beyond that provided by air sampling alone.

The reference values most commonly used in this case are guidelines such as the annually revised Biological Exposure Indices (BEIs), published by the ACGIH. BEIs, like the TLVs, RELs and PELs, do not represent a sharp distinction between hazardous and non-hazardous exposures. The ACGIH Documentation of the BEIs states: “Alterations in function or unusual laboratory findings can be viewed as evidence of harm, or they can be viewed as only a marker that exposure has occurred. Interpretation of biological monitoring is complicated by the fact that the concentration of the material measured is not exactly equivalent of the exposure dose. When a chemical is absorbed into the body, excretion of earlier ingestion of that substance may be occurring at the same time.” Action on unexpected values should not be based on a single isolated measurement but on measurements of multiple sampling.

There are 36 compounds for which BEIs have been established. These 36 compounds are listed in Table 1, along with the biological matrix used for their evaluation. BEIs listed in that table are established by the ACGIH. Additional information on these guidelines can be obtained from that organization (see Resource List at end of this Guide). The BEI values should be used only by a medically-trained individual familiar with their interpretation, and then only with the aid of the documentation for BEIs which is also available from the ACGIH.


Table 1. Chemicals with Established BEIs
Chemical Biological Specimen Chemical Biological specimen
Acetone Urine Methanol Urine
Analine Urine or blood Methemoglobin inducers Blood
Arsenic Urine Methoxyethanol Urine
Benzene Urine Methoxyethyl acetate Urine
Cadmium Urine or blood Methyl chloroform Exhaled air, urine or blood
Carbon disulfide Urine Methylene bis(2-chloroaniline) Urine
Carbon monoxide Blood or exhaled air Methyl ethyl ketone Urine
Chlorobenzene Urine Methyl isobutyl ketone Urine
Chromium Urine Nitrobenzene Urine or blood
Cobalt Urine or blood Organophosphorus  
Dimethylacetamide Urine cholinesterase inhibitors Blood
Dimethylformamide Urine Parathion Urine or blood
Ethoxyethanol Urine Pentachlorophenol Urine or blood
Ethoxyethyl acetate Urine Perchloroethylene Exhaled air, urine or blood
Ethyl benzene Urine or exhaled air Phenol Urine
Fluorides Urine Styrene Urine or blood
Furfural Urine Toluene Urine or blood
Hexane Urine or exhaled air Tricholorethylene Urine, blood or exhaled air
Lead Blood Vanadium Pentoxide Urine
Mercury Urine or blood Xylenes Urine

Critical Factors for Biological Monitoring

1. The timing of the sample collection is critical, and the protocol guidelines must be followed. This is because different chemicals and their markers take different times to make themselves available for sampling in the same body medium, as characterized by their half-life. The BEI measurements may be intended to represent peak exposures, or to reflect equilibrium levels attained only after steady state has been reached.

2. When interpreting biological monitoring data, the physician must take into consideration factors that contribute to individual variation in response to the exposure. You and your colleagues will likely have differences in pulmonary function, hemodynamics, body composition, efficacy of excretory organs, and activity of enzyme systems that mediate metabolism of the chemical. Other factors to consider include personal factors (age, sex, pregnancy, medications, state of health), lifestyle choices (smoking, drug use, eating habits, and personal hygiene), and environmental exposures outside the workplace. It is possible to exceed the BEIs and not experience adverse health effects. Your personal or company physician must carefully evaluate your personal profile and integrate all necessary information into the interpretation of biological monitoring results.

3. To assist in the interpretation of biological monitoring, particularly the BEIs, the physician is referred to the ACGIH Documentation of the BEIs which detail specific information on the above variables as they relate to a specific chemical agent, and lists quality control measures to be taken in the sampling, handling, and analysis of specimens.

When is biological monitoring necessary or appropriate?

1. Specific monitoring may be mandated by an OSHA standard (Table 2), or may be recommended by the documentation of a specific BEI.

2. The effectiveness of personal protective equipment (or even personal hygiene, work practices, and engineering controls) in creating a barrier against the hazardous agent can be evaluated through monitoring for the marker of the exposure. For example, airborne concentrations of inorganic arsenic may be undetectable in the breathing zone during handling of treated objects. However, high concentrations in the urine may indicate inadvertent ingestion though lack of gloves and poor hand or face washing practices.

3. Biological monitoring should be used to substantiate air monitoring, or to determine the potential for absorption via the skin and GI tract. It should be conducted when it offers an advantage over the use of air monitoring alone.

When should biological monitoring not be used?

Biological monitoring should not be used as your personal exposure control method, because it measures dose only after it has occurred and may affect bodily functions in some way. Biological monitoring and medical surveillance are not substitutes for environmental or personal sampling but should be used to complement them.


Table 2. OSHA Standards with Medical Examination or Surveillance Requirements, Title 29 Code of Federal Regulations (CFR) Part 1910
1910.95   Occupational noise exposure
1910.134   Respiratory protection
1910.139   Respiratory protection for M. tuberculosis
1910.1001   Asbestos (and 1926.1101 – Asbestos in Construction Industry)
1910. 1003   Select Carcinogens
   
4-Nitrobiphenyl
alpha-Naphthylamine
Methyl chloromethyl ether
3,'-Dichlorobenzidine (and its salts)
bis-Chloromethyl ether
beta-Naphthylamine
Benzidine
4-Aminodiphenyl
Ethyleneimine
beta-Propiolactone
2-Acetylaminofluorene
4-Dimethylaminoazo-benzene
N-Nitrosodimethylamine
1910.1017   Vinyl chloride
1910.1018   Inorganic arsenic
1910.1025   Lead
1910.1027   Cadmium
1910.1028   Benzene
1910.1029   Coke oven emissions
1910.1030   Bloodborne pathogens
1910.1043   Cotton dust
1910.1044   1,2-dibromo-3-chlorpropane
1910.1045   Acrylonitrile
1910.1047   Ethylene oxide
1910.1048   Formaldehyde
1910.1050   Methylenedianiline
1910.1051   1,3-Butadiene
1910.1052   Methylene chloride
1910.1450   Occupational exposure to hazardous chemicals in laboratories

Medical Monitoring

Medical monitoring is conducted on exposed individual to evaluate any adverse health effects of those exposures. The major purpose is the early detection of disease or conditions for which treatment can prevent further illness. Health surveillance of a population of workers for disease is used to predict effect and can also be a valuable tool in hazard control, by detecting when an initially effective control or work practice has lost effectiveness.

Recommendations for medical monitoring tests are in the purview of the physician, based on reported symptoms and knowledge (provided by the conservator) of chemicals to which the patient is exposed. Be respectful of the fact that physicians receive a standardized medical school education, and that occupational and environmental medicine is considered a specialty requiring further training in epidemiology, toxicology, industrial hygiene, and case management of occupational injuries and illnesses. Physicians specializing in occupational medicine are certified by the American Board of Preventive Medicine. Additional medical resources can be found on the attached listing of Occupational Health Clinics, as published by the Association of Occupational and Environmental Clinics

Many OSHA standards now have requirements for medical examinations, focusing on screening of individuals or surveillance of an entire exposed group. These standards are listed in Table 2.

Highlights for Conservators: The OSHA Respiratory Protection Standard

The OSHA Respiratory Protection Standard 29CFR1910.134 requires medical approval prior to use of a respirator for a number of reasons, all relating to fitness-for-duty. For example: can a firefighter stand the physical and physiological strain of wearing a self-contained breathing apparatus? Does the worker have pre-existing medical conditions which can be worsened by the effect of wearing a respirator (claustrophobia, severe asthma or pulmonary disease)? Should the individual be working in a certain chemical exposure setting (even with a respirator, which is not infallible) if they have a compromised immune system, are pregnant, or have other medical conditions for which the PELs or TLVs might not apply?

Periodic (typically, annual) follow-up respirator medical examinations are also useful to review current exposure data and any changes in personal medical history. Abnormal pulmonary function tests or chest x-rays may indicate a compromised or ill-fitting respirator, or a hyper-susceptible individual for whom a respirator should not be approved as the primary control.

Attached is the Medical Evaluation Questionnaire (mandatory Appendix C of the OSHA Respiratory Protection Standard), which is to be used by your physician to evaluate and approve your ability to wear a respirator in the course of your duties.

Medical monitoring is conducted on exposed individual to evaluate any adverse health effects of those exposures. The major purpose is the early detection of disease or conditions for which treatment can prevent further illness. Health surveillance of a population of workers for disease is used to predict effect and can also be a valuable tool in hazard control, by detecting when an initially effective control or work practice has lost effectiveness.

Recommendations for medical monitoring tests are in the purview of the physician, based on reported symptoms and knowledge (provided by the conservator) of chemicals to which the patient is exposed. Be respectful of the fact that physicians receive a standardized medical school education, and that occupational and environmental medicine is considered a specialty requiring further training in epidemiology, toxicology, industrial hygiene, and case management of occupational injuries and illnesses. Physicians specializing in occupational medicine are certified by the American Board of Preventive Medicine. Additional medical resources can be found on the attached listing of Occupational Health Clinics, as published by the Association of Occupational and Environmental Clinics

Many OSHA standards now have requirements for medical examinations, focusing on screening of individuals or surveillance of an entire exposed group. These standards are listed in Table 2.

Highlights for Conservators: The OSHA Respiratory Protection Standard

The OSHA Respiratory Protection Standard 29CFR1910.134 requires medical approval prior to use of a respirator for a number of reasons, all relating to fitness-for-duty. For example: can a firefighter stand the physical and physiological strain of wearing a self-contained breathing apparatus? Does the worker have pre-existing medical conditions which can be worsened by the effect of wearing a respirator (claustrophobia, severe asthma or pulmonary disease)? Should the individual be working in a certain chemical exposure setting (even with a respirator, which is not infallible) if they have a compromised immune system, are pregnant, or have other medical conditions for which the PELs or TLVs might not apply?

Periodic (typically, annual) follow-up respirator medical examinations are also useful to review current exposure data and any changes in personal medical history. Abnormal pulmonary function tests or chest x-rays may indicate a compromised or ill-fitting respirator, or a hyper-susceptible individual for whom a respirator should not be approved as the primary control.

Attached is the Medical Evaluation Questionnaire (mandatory Appendix C of the OSHA Respiratory Protection Standard), which is to be used by your physician to evaluate and approve your ability to wear a respirator in the course of your duties.

The Value of the Exposure Assessment: Everyone Has a Part to Play

An exposure assessment relies on judgement and contributions from all parties involved. The conservator can provide the industrial hygienist and/or physician with a detailed chemical inventory and Material Safety Data Sheets. This list should include hazards that are known to be inherent to the objects you typically work with, such as white lead in paintings or mold growth on paper and books. The health professionals will also need to understand the routine and non-routine tasks involved, including all tasks and movements that might produce peak exposures, and any existing controls. Understanding your work exposure time frame is critical for a physician to administer clinical tests he/she thinks are useful. For example, if a physician believes that biological monitoring for lead exposure appears warranted for a paintings conservator, he/she will need to know if the blood tests reflect exposure in the preceding few days, or accumulated exposure that ended months ago. If your physician is not specialized in occupational medicine, provide her/him with copies of the appropriate OSHA standard (see Table 2, and access standard on the Internet or by phone from OSHA), particularly the medical surveillance technical appendices, and the ACGIH references for BEIs.

If an overexposure is indicated, the health professional will need to expand the assessment to evaluate the effectiveness of existing ventilation or work practice controls, and take further action. Instituting a permanent control (i.e., change in chemical, installation of ventilation controls) is the best option. Interim controls would include the use of a respirator and/or other properly selected personal protective equipment. Another interim option would involve "administrative" controls, such as the rotation of staff through the problematic task, with the intent to reduce everyone's average daily exposure to a minimal concentration. Exposure control is not the topic of this Guide; however, the reader should consult the Resources for further direction.

There are many important and useful reasons to justify the expense of determining the exposure risks presented by your conservation tasks, and the most reasonable control plans to reduce these exposures. The most important reason, of course, is to prevent illness in you and your colleagues.

Acknowledgements

The AIC Health and Safety Committee wishes to acknowledge the assistance of Dr. G. Edward Burroughs, Ph.D., CIH, and Kathryn A. Makos, MPH, CIH, in the compilation of this Guide. Dr. Burroughs is a Research Industrial Hygienist with the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, of the U.S. Public Health Service. Ms. Makos is a senior industrial hygienist with the Office of Environmental Management and Safety, Smithsonian Institution.

Resources

American Conference of Governmental Industrial Hygienists. 1330 Kemper Meadow Drive, Cincinnati, OH 45240; 513-742-2020; http://www.acgih.org/.

Association of Occupational and Environmental Clinics; 1010 Vermont Ave., NW #513, Washington DC 20005; 202-347-4976.

National Institute for Occupational Safety and Health (NIOSH); 800-356-4647; www.cdc.gov/niosh

Occupational Safety and Health Administration (OSHA); 200 Constitution Ave NW, Washington DC, 20210; 202-219-8148; http://www.osha.gov/

References

ACGIH. 1998. Documentation of the Threshold Limit Values and Biological Exposure Indices. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists.

DiNardi, S. R., ed. 1997. The occupational environment - its evaluation and control. Fairfax, Virginia: American Industrial Hygiene Association Press. 262-282.

Ho, M. H. and H. K. Dillon. 1987. Biological monitoring of exposure to chemicals, organic compounds. New York, NY: John Wiley & Sons.

Mulhausen, J. R. and J. Damiano. 1998. A strategy for assessing and managing occupational exposure, 2nd ed. Fairfax, Virginia: American Industrial Hygiene Association Press.

Plog, B.A., ed. 1996. Fundamentals of industrial hygiene, 4th ed. Chicago, IL: National Safety Council.




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