Health hazards, common toxic chemicals

The potential health hazard to an individual by a material used in any chemical process is a function of the inherent toxicity of the material and the frequency and duration of exposure, ft is common practice to distinguish between the short-term and long-term effects of a materiaf. A highly toxic material that causes immediate injury is classified as a safety hazard while a material whose... 

Biomonitoring for human health hazard surveillance typically involves collection of hair, expired air, bodily fluids (blood, urine, saliva, breast milk, semen), feces, epithelial scrapings, exfoliated cells, or, less frequently, tissue biopsies from people known or suspected of being exposed to potential chemical, physical, or biological hazards. These samples are analyzed for toxic chemicals, their metabolites, or biomarker responses. The most commonly used biomarkers in humans are those relating to DNA and chromosomal damage, because these effects contribute to cancer risk. Besides biomarkers of chemical exposure and effects, there are also human biomarkers of tumor formation and susceptibility to toxic... 

Over 80 000 chemicals are listed in the TSCA registry, with 1500-2500 new chemicals added each year 20 000 chemicals are commonly found in the workplace (NIOSH list) with <1% tested for reproductive and developmental hazard potential. It is therefore necessary and appropriate to develop fast, inexpensive, sensitive, and accurate methods to prescreen the plethora of chemicals and concentrate resources on those identified by the screening test(s) as potential human health hazards. However, the mechanisms of action of developmental toxicants appear numerous and frustratingly difficult to identify (see section Mechanisms). 

This element is a chalcophile, and in unweathered rocks is most commonly found as the mineral cinnabar (HgS). In soil environments, the cationic form, is most common, as the reduced oxidation state (+1) has a limited stability range. Reduction to the metallic elemental form, H, is easily achieved in soils by both biological and chemical reactions. Elemental mercury is somewhat volatile, and the vapor is extremely toxic to organisms. Under anaerobic conditions at least, soil microbes methylate mercury, forming volatile organomercury compounds that are bioavail-able and present a health hazard. At the same time, however, anaerobic conditions can convert Hg into the exceedingly insoluble sulhde, HgS. Some of the more important transformations possible for mercury in soil are summarized in Figure 9.9. 

We would not use the additive model for contaminants to substances or chemicals in a mixture that do not share a common toxic endpoint. A hazard index equal to 1.0 for a mixture is analogous to the HS for an individual contaminant. Therefore, a hazard index greater than 1.0 indicates that the mixture exceeds the health risk limit. Contaminants that have more than one toxicological endpoint listed should be included in all the appropriate toxicological endpoint groups. Group the contaminants in the mixture according to the health effects they cause. 

Basic information on the toxicity of many of the most commonly encountered and tox-icologically significant industrial chemicals is provided in Table IV-4. The table Is Intended to expedite the recognition of potentially hazardous exposure situations and therefore provides infomiation such as vapor pressures, warning properties, physical appearance, occupational exposure standards and guidelines, and hazard classification codes, which may also be useful in the assessment of an exposure situation. Table IV-4 is divided into 3 sections health hazards, exposure guidelines, and comments. To use the table correctly, it is important to understand the scope and limitations of the information it provides. 

The NFPA health hazard rating is based on both the intrinsic toxicity of a chemical and the toxicities of its combustion or breakdown products. The overall ranking is determined by the greater source of health hazard under fire or other emergenr conditions. Common hazards from the ordinary combustion of materials are not considered in these rankings. 

Adhesion requires the use of a variety of compounds that may be safe, hazardous, flammable, or form hazardous waste. Table 13.5 provides a partial list of some of the more commonly used chemicals. There has been extensive collaboration between the industry and the governmental environmental protection agencies to reduce all emissions. For instance, the Design for Environment (DfE) program in the Environmental Protection Agency s (EPA) Office of Pollution Prevention and Toxics has been a voluntary partnership with the industry to develop and distribute pollution prevention and environmental and human health risks on alternative chemicals, processes, and products. The DfE approach uses cleaner technologies... 

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