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 2. Procedures should not threaten the health of the participant.

3. Risk of using invasive methods must be justified by the benefits.

4. Informed consent from the participant is required. This consent must be given when the participant feels no fear of reprisals, if consent is withheld. 5. Results should be kept confidential and shared only with the occupational health professional and the participant.

Laboratory Safety. When dealing with human specimens, a biosafety program is essential. Pathogens such as hepatitis B and human immunodeficiency virus (HIV) may be present in blood, saliva, semen, and other body fluids. Transmission can be by an accidental nick with a sharp object; exposure through open cuts, skin abrasions, and even dermatitis or acne; and indirectly through contact with a contaminated environmental surface. There are five major ways to reduce the potential for exposure to biological pathogens [32, 33]:

1. Engineering controls, which include mechanical or physical systems used to eliminate biological hazards, must be available. These are items such as biosafety cabinets or self-sheathing needles.

2. Employee work practices are essential to minimize exposure to pathogens. Good personal hygiene procedures and avoidance of needle recapping can lessen exposure to pathogens.

3. Personal protective equipment, such as gloves and masks, should be used when necessary.

4. Good housekeeping procedures, which involve cleanup of the work area, are essential to avoid contamination of the laboratory.

5. Employees, who have been identified as potential exposure candidates, should be vaccinated for hepatitis B.

Universal precautions that take into account the above five measures should be practiced with every biological sample received. It is not possible to know if a particular sample may contain pathogens; therefore, each sample should be treated as if contaminated.

4. INTERPRETATION OF RESULTS

A biological monitoring analytical result is a determination of the level of the biomarker in the biological matrix from which the sample was taken, at the time it was taken. Extrapolation from that datum to insight on the exposure of the worker requires knowledge of how the human body responds to the agent.

1. Exposure can be estimated when a quantitative relationship between environmental level and biomarker level has been demonstrated.

2. Health risk can be estimated when a quantitative relationship between a health effect and biomarker level has been demonstrated.

3.Where knowledge of a biomarker is limited, one can only infer from its presence above the background level that exposure has occurred.

Reference Levels. For a number of agents there exist published reference levels, termed "biological action levels" by the World Health Organization [18], which serve as guidelines for interpreting biological monitoring data. In the absence of published biomonitoring action levels, biomarker levels 1/15/98 Manual of Analytical Methods