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Biological exposure indices
Biological exposure indices Laboratory Health & Safety
B
Doug Walters, former head of laboratory health and safety for the National Toxicology Program (NTP), now consults and writes on Laboratory and Chemical Health and Safety in Raleigh, NC and can be reached at waltersdb@ earthlink.net.
1074-9098/00/$20.00 PII S1074-9098(00)00190-8
iological exposure indices (BEI) are values used for guidance to assess biological monitoring results. The American Conference of Governmental Industrial Hygienists publishes a yearly updated list of approximately 30 chemicals with BEIs (ACGIH, TLV and BEIs, Cincinnati, OH). With respect to chemical exposure, biological monitoring is the measurement of the concentration of a chemical marker in a human biological media that indicates exposure. This is most easily and unobtrusively done with certain human fluids and tissues such as, blood, urine, feces, saliva, earwax, milk, sperm, tears, sputum, sweat, expired air, nails, hair, skin and sometimes fat. Sampling is difficult if internal organs must be sampled. The markers measured may include the actual chemical, a metabolite or degradation product, and biochemical reaction product or response (e.g., antigen, enzyme, antibody). The detection and concentration of a marker is indicative of exposure. The difference between biological monitoring and medical surveillance was discussed in an earlier column (CH&S, 1996, 3(6), 8). BEI tables precisely list 4 factors, the determinate, sampling time, determinant concentration, and additional remarks. The determinant is the actual substance analyzed and the body fluid in which it is measured, e.g., methemoglobin in blood for aniline, t,t-muconic acid in urine for benzene. Sampling time specifies when sampling must be done, e.g., before, during, or after a shift or workweek. Sampling time details are also defined. For example, prior to shift means 16 hours after exposure ceases, during shift is anytime after 2 hours exposure, end of shift is immediately after exposure ceases, end of workweek is after 4 or 5 consecutive work days of exposure, and discretionary means any time. Special attention needs to be given to the units of concentration of the BEI. Units are expressed as concentration of the specific determinant in the biological matrix, for example, mg/L in urine or blood, mg/g creatinine in urine, ppm in expired air, % of hemoglobin in blood. Finally, specific additional remarks are given using four abbreviations, B, Nq, Ns, and Sq, B means the determinant may be present in the background of non-occupationally exposed persons. Nq is used to indicate that a
specific BEI could not be determined, but that biological monitoring should be considered for the chemical. Ns indicates the determinant is nonspecific and can be detected after exposure to other chemicals. Sq means the data is semi-quantitative and the information should only be used to indicate possible exposure. There are few OSHA standards like the Lead Standard (29 CRF 1910.1025) that specify criteria for biological monitoring. Similarly, it is important to understand that the presence of a BEI does not mean that biological monitoring should be conducted. Existence of a BEI simply means that an established, validated procedure exists to conduct biological monitoring and that the monitoring results have been reliably correlated to general worker exposure. Many chemicals have biological monitoring methods in the literature. However, because of interference, masking, limits of detection and a host of other reasons, few methods have not been correlated and validated like BEIs in terms of workplace exposure. BEIs are established at concentrations below which workers should not generally experience adverse health effects. Single measurement should never be used to declare a safe workplace. Whenever BEIs are used, special attention should be given to quality assurance, privacy and confidentiality, and informing the donor of the results. Special attention should always be given to the specimen, donor history and background, collection time, exposure time, storage conditions, container used, labeling, analytical method, laboratory accreditation, method sensitivity, and limits of detection. Attention also needs to be given to ethical considerations when biological monitoring is contemplated. The safety professional must have a close working relationship and communicate well with the analytical laboratory, the occupational physician, and corporate lawyers from the beginning. In all cases, qualifications, experience, and training are crucial. Conflicts, masking and interference between workplace and non-workplace environments and other chemicals are common concerns when performing biological monitoring. It is always wise to consult the ACGIH, Documentation of the Threshold Limit Values and Biological Indices for complete information on specific BEIs.
© Division of Chemical Health and Safety of the American Chemical Society Published by Elsevier Science Inc.
29
B
Doug Walters, former head of laboratory health and safety for the National Toxicology Program (NTP), now consults and writes on Laboratory and Chemical Health and Safety in Raleigh, NC and can be reached at waltersdb@ earthlink.net.
1074-9098/00/$20.00 PII S1074-9098(00)00190-8
iological exposure indices (BEI) are values used for guidance to assess biological monitoring results. The American Conference of Governmental Industrial Hygienists publishes a yearly updated list of approximately 30 chemicals with BEIs (ACGIH, TLV and BEIs, Cincinnati, OH). With respect to chemical exposure, biological monitoring is the measurement of the concentration of a chemical marker in a human biological media that indicates exposure. This is most easily and unobtrusively done with certain human fluids and tissues such as, blood, urine, feces, saliva, earwax, milk, sperm, tears, sputum, sweat, expired air, nails, hair, skin and sometimes fat. Sampling is difficult if internal organs must be sampled. The markers measured may include the actual chemical, a metabolite or degradation product, and biochemical reaction product or response (e.g., antigen, enzyme, antibody). The detection and concentration of a marker is indicative of exposure. The difference between biological monitoring and medical surveillance was discussed in an earlier column (CH&S, 1996, 3(6), 8). BEI tables precisely list 4 factors, the determinate, sampling time, determinant concentration, and additional remarks. The determinant is the actual substance analyzed and the body fluid in which it is measured, e.g., methemoglobin in blood for aniline, t,t-muconic acid in urine for benzene. Sampling time specifies when sampling must be done, e.g., before, during, or after a shift or workweek. Sampling time details are also defined. For example, prior to shift means 16 hours after exposure ceases, during shift is anytime after 2 hours exposure, end of shift is immediately after exposure ceases, end of workweek is after 4 or 5 consecutive work days of exposure, and discretionary means any time. Special attention needs to be given to the units of concentration of the BEI. Units are expressed as concentration of the specific determinant in the biological matrix, for example, mg/L in urine or blood, mg/g creatinine in urine, ppm in expired air, % of hemoglobin in blood. Finally, specific additional remarks are given using four abbreviations, B, Nq, Ns, and Sq, B means the determinant may be present in the background of non-occupationally exposed persons. Nq is used to indicate that a
specific BEI could not be determined, but that biological monitoring should be considered for the chemical. Ns indicates the determinant is nonspecific and can be detected after exposure to other chemicals. Sq means the data is semi-quantitative and the information should only be used to indicate possible exposure. There are few OSHA standards like the Lead Standard (29 CRF 1910.1025) that specify criteria for biological monitoring. Similarly, it is important to understand that the presence of a BEI does not mean that biological monitoring should be conducted. Existence of a BEI simply means that an established, validated procedure exists to conduct biological monitoring and that the monitoring results have been reliably correlated to general worker exposure. Many chemicals have biological monitoring methods in the literature. However, because of interference, masking, limits of detection and a host of other reasons, few methods have not been correlated and validated like BEIs in terms of workplace exposure. BEIs are established at concentrations below which workers should not generally experience adverse health effects. Single measurement should never be used to declare a safe workplace. Whenever BEIs are used, special attention should be given to quality assurance, privacy and confidentiality, and informing the donor of the results. Special attention should always be given to the specimen, donor history and background, collection time, exposure time, storage conditions, container used, labeling, analytical method, laboratory accreditation, method sensitivity, and limits of detection. Attention also needs to be given to ethical considerations when biological monitoring is contemplated. The safety professional must have a close working relationship and communicate well with the analytical laboratory, the occupational physician, and corporate lawyers from the beginning. In all cases, qualifications, experience, and training are crucial. Conflicts, masking and interference between workplace and non-workplace environments and other chemicals are common concerns when performing biological monitoring. It is always wise to consult the ACGIH, Documentation of the Threshold Limit Values and Biological Indices for complete information on specific BEIs.
© Division of Chemical Health and Safety of the American Chemical Society Published by Elsevier Science Inc.
29