Sources and Exposures

Areas in the vicinity of zinc mines and smelters often show pronounced Cd contamination [2,5]. Until the 1920s the industrial use of Cd was limited, but the world Cd production has increased steadily to 20,000 tons/year in the 1980s, 

Cd waste enters the air, water, and soil through industrial and household wastewater and waste incineration, burning of fossil fuels, and biomass. The primary form of Cd in occupational exposures is Cd oxide (CdO), which is predominantly inhaled from industrial dust and fumes. Improved technologies and regulations mean little Cd now enters air and water in Western Europe or Northern America. But it is still a major source of contamination in developing and newly industrializing countries. 

Besides smoking, the major route of Cd intake for non-occupationally exposed humans is through food or water. Cd in drinking water contributes only to less than a few percent of the total Cd intake [8] with the exception of heavily contaminated areas. Food is the major source of Cd for the general population, which is particularly caused by the use of phosphate rock (as opposed to processed phosphoric acid and phosphate fertilizers) for agricultural purposes because most natural and agricultural soils are phosphate-deficient and plants require phosphate for growth. 

Compared to those of igneous origin, phosphate rock deposits of sedimentary origin contain higher levels of Cd and are the raw material used in the manufacture of most commercial phosphate fertilizers. In 2009, the world s largest producers of 

The CONTAM report from the European Food Safety Authority recently concluded that across Europe the average dietary intake of Cd in adults is between 1.9 and 3.0 pg/kg b.w. per week, and can even reach 2.5-3.9 pg/kg b. w. per week in highly exposed adults [3] (http //www.efsa.europa.eu/en/efsajoumal/doc/980.pdf). This intake is close to or slightly exceeding the threshold value of 2.5 pg/kg b.w. per 

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No tests available, but history may help to identify source and exposure characteristics (majority of incidents generating exposures to humans involve trucking with labels on vehicle). 

The two ultimate sources of chemicals - nature and industrial and laboratory synthesis - are then briefly described. This review sets the stage for a discussion of how human beings become exposed to chemicals. The conditions of human exposure are a critical determinant of whether and how a chemical will produce injury or disease, so the discussion of chemical sources and exposures naturally leads to the major subject of the book - the science of toxicology. 

Zhang, J., Q. He, and P. J. Lioy, "Characteristics of Aldehydes Concentrations, Sources, and Exposures for Indoor and Outdoor Residential Microenvironments, Environ. Sci. TechnoL, 28, 146-152 (1994a). 

Several factors need to be kept in mind concerning x-ray resist design. Firstly, source design has mainly utilized electron bombardment of the target material to generate x-rays. Power output is limited by heat transfer considerations, and when account is also taken of the separation between source and exposure plane (wafer) as necessitated by geometrical considerations, it... 

Peters, S.C., Blum, J.D., Karagas, M.R. et al. (2006) Sources and exposure of the New Hampshire population to arsenic in public and private drinking water supplies. Chemical Geology, 228(1-3 Special Issue), 72-84. 

Wilford, B.H., Shoeib, M., Hamer, T., Zhu, J. and (ones, K.C. (2005) Polybrominated diphenyl ethers in indoor dust in Ottawa, Canada implications for sources and exposure. Environmental Science and Technology, 39, 7027-35. 

Aggregate exposure assessment is naturally more complex than the methods used for dietary risk assessment. In the simplest analysis a worst case can be established for each source and exposure route and then summed to give a total exposure. If this were below any threshold of concern such as the PTWI then no further action would be required. However, if the total worst case exposure was above a PTWI then it is unlikely to reflect the real situation since the probability that any individual would be exposed to each source by each route at the maximum level is very remote. 

Zhang J, He Q, Lioy PJ. 1994a. Characteristics of aldehydes Concentrations, sources, and exposures for indoor and outdoor residential microenvironments. Environ Sci Technol 28 146-152. 

Trudel and his co-workers also observed that product-related exposure tends to be more important for PFOA than for PFOS, most likely because PFOS is no longer used in consumer products. It is, therefore, apparent that the paucity of indoor source and exposure data contributes to the significant uncertainty and differences of opinion about the most prevalent exposure routes for these compounds. 

Table 5.3-3 Radiation sources and exposure techniques for higher resolution ...

The Twenty-Fifth Annual Conference on Trace Substances in Environmental Health was held at the University of Missouri, May 20-23, 1991. Findings and recommendations conclude that (1) lead is ubiquitous in the human environment (2) any lead exposure assessment must analyze all potential sources and exposure pathways and (3) acceptable soil lead levels can be determined only through an approach that takes into account numerous factors including but not limited to the population at risk, the physical availability of the lead, and the bioavailability of the lead, which is the amount of lead that can be ingested into the blood stream. 

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