Hazardous substances carcinogenicity

For hazardous substances not classified as carcinogens, where protection of exposure is not reasonably practicable, adequate control should be achieved by measures odier than personal protection, so far as is reasonably practicable. Tliis is subject to the degree of exposure, circumstances of use of the substance, informed knowledge about the hazards and current technical developments. Any combination of the measures listed in Table 5.22 are applicable. 

Table 5.22 Measures for the control of exposure to hazardous substances not classified as carcinogens...

OSHA maintains a list of potential carcinogens. In addition, OSHA sets enforceable permissible exposure limits (PELS) to protect workers against the health effects of exposure to hazardous substances. 

OSHA. 1996. Occupational safety and health standards. Toxic and hazardous substances. 13 Carcinogens (4-Nitrobiphenyl, etc.). Occupational Safety and Health Administration. U.S. Department of Labor. Code of Federal Regulations. 29 CFR 1910.1003. 

The term hazardous substance refers to any raw materials, intermediate products, final products, spent wastes, accidental spills, leakages, and so on, that are hazardous to human health and the environment. Technically speaking, aU ignitable, corrosive, reactive (explosive), toxic, infectious, carcinogenic, and radioactive substances are hazardous [1-3]. 

Aromatic amines, substituted hydrazines and their derivatives. These should all be treated as potentially carcinogenic, and as a group probably constitute the greatest danger to the organic chemist since even a slight exposure may initiate the formation of tumours. The following list includes some of the most hazardous substances. 

The classification system must apply to waste that contains carcinogenic and noncarcinogenic hazardous substances. Therefore, classification of waste based on risk must take into account the different forms of the assumed dose-response relationships for these two types of substances (response proportional to dose, without threshold, for carcinogens threshold for noncarcinogens). 

Risk is not always a useful measure of health impact in evaluating the risk index, because risk is not proportional to dose when a hazardous substance is assumed to have a threshold dose-response relationship. For this type of substance, the risk is presumed to be zero at any dose below a nominal threshold. Since the allowable dose of such substances should always be less than the threshold in order to prevent the occurrence of adverse responses, expressing the risk index in terms of risk would result in an indeterminate value when the dose is below the threshold and, more importantly, a lack of distinction between doses near the nominal thresholds and lower doses of much less concern. For any hazardous substance, including carcinogens for which risk is assumed to be proportional to dose without threshold, a generally useful form of risk indexes (Rid is in terms of dose ... 

Adding risk indexes (RR) for noncarcinogenic substances and combining risk indexes (RR) for carcinogenic and noncarcinogenic substances requires care, however, due to the assumed forms of the dose-response relationships. The evaluation of Equation 1.3 for mixtures of hazardous substances is described in Section I.5.5.4. 

The risk index for any hazardous substance in Equation 1.1 or 1.2 (see Section 1.5.1) is calculated based on assumed exposure scenarios for hypothetical inadvertent intruders at near-surface waste disposal sites and a specified negligible risk or dose in the case of exempt waste or acceptable (barely tolerable) risk or dose in the case of low-hazard waste. Calculation of the risk index also requires consideration of the appropriate measure of risk (health-effect endpoint), especially for carcinogens, and the appropriate approaches to estimating the probability of a stochastic response per unit dose for carcinogens and the thresholds for deterministic responses for noncarcinogens. Given a calculated risk index for each hazardous substance in a particular waste, the waste then would be classified using Equation 1.3. 

Risk Index for Mixtures of Hazardous Substances. For the purpose of developing a comprehensive and risk-based hazardous waste classification system, a simple method of calculating the risk posed by mixtures of radionuclides and hazardous chemicals is needed. The method should account for the linear, nonthreshold dose-response relationships for radionuclides and chemical carcinogens (stochastic effects) and the threshold dose-response relationships for noncarcinogenic hazardous chemicals (deterministic effects). 

Second, not all chemical wastes that contain hazardous substances are deemed to be hazardous. EPA considers wastes that contain certain hazardous substances (heavy metals and organic compounds, including carcinogens and noncarcinogens) not to be hazardous if the leachability of the substances from the waste form is limited. This characterization of waste as nonhazardous is based on EPA s judgment that potential risks to humans resulting from disposal of the waste would not exceed acceptable levels. 

For any hazardous substance, estimates of the relationship of dose to response in humans are based on either animal or human data. For example, only about 20 of the approximately 300 chemical carcinogens regulated by EPA have dose-response relationships based on human data from epidemiologic studies the remainder are based on animal bioassays. In contrast, the dose-response relationships for radiation are based primarily on the results of human epidemiologic studies. 

Two of the standards directly related to worker health and important in design work are Toxic Hazardous Substances and Occupational Noise Exposure. The first of these two concerns the normal release of toxic and carcinogenic substances, carried via vapors, fumes, dust fibers, or other media. Compliance with the Act requires the designer to make calculations of concentrations and exposure time of plant personnel to toxic substances during normal operation of a process or plant. These releases could emanate from various types of seals and from control-valve packings or other similar sources. Normally, the designer can meet the limits set for exposure to toxic substances by specifying special valves, seals, vapor-recovery systems, and appropriate ventilation systems. 

CONSENSUS REPORTS NTP 10th Report on Carcinogens. lARC Cancer Review Group 2B IMEMDT 7,56,87 Animal Sufficient Evidence IMEMDT 39,41,86. EPA Extremely Hazardous Substances List. Community Right-To-Know List. Reported in EPA TSCA Inventory. 

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