Page 373 - Industrial Ventilation Design Guidebook

328 CHAPTER 5 PHYSIOLOGICAL AND TOXICOLOGICAL CONSIDERATIONS

TABLE 5.23 Biomonitoring Serves Three Different Purposes of
Identifying and Using

1. Biomarkers for susceptibility of an individual within a population of
one species to exposure to an intoxicant—genetically determined
susceptibility.
2. Biomarkers for internal dose of the intoxicant—dose monitoring.
3. Biomarkers for early biological changes following exposure— effect
monitoring.
Source: Modified from Aldridge. 64

2. Hazard characterization and delineation of dose-effect or dose-
response relationships
3. Assessment of exposure
4. Risk characterization
Risk characterization should preferentially include qualitative and, if pos-
sible, also quantitative risk assessment based on steps 1-3.
Hazard identification, step one, means identification of new chemicals
or other factors that may cause harmful health effects. Previously, novel
hazards were usually observed in case studies or after accidents or other
excessive exposures, usually in occupational environments. Today, thor-
ough toxicity studies are required on all pesticides, food additives, and
drugs. New chemicals also have to be studied for their potential toxic ef-
fects. Thus, earlier hazards were in most cases identified after they had
caused harmful effects in humans. Today, most chemical products have
been evaluated for their toxicity with experimental animals. Therefore,
hazard identification has become a preventive procedure based on safety
studies conducted before a chemical compound or product reaches the
market, and before individuals are exposed to it. 49
Hazard characterization, step two, usually utilizes data from toxicity
studies with experimental animals. In step one, compounds that have to be
studied for their toxicity were briefly described. Health authorities in different
countries have issued strict guidelines and regulations on the studies that have
to be carried out to evaluate the toxicity of pesticides, food additives, and
drugs. Furthermore, the European Union and the OECD have issued regula-
tions that are followed in these countries. For example, in the United States,
the U.S. Environmental Protection Agency and Food and Drug Administration
carefully control the safety of drugs, food additives, pesticides, and other
chemicals. The technical quality of the studies has been regulated in detail by
good laboratory practice (GLP) guidelines. In Table 5.24, the toxicity/safety
studies utilizing experimental animals or other test systems required for the
registration of drugs, pesticides, and food additives have been listed. 49
Exposure assessment, step three, allows a risk assessor to estimate the sig-
nificance of the effects induced by high doses of a chemical in experimental
animals in a human situation. Exposure assessment is, in fact, a prerequisite
for quantitative risk assessment because it allows a comparison between ef-
fects induced by high dose with those induced by low doses, and also allows