Occupationally exposed individuals

Several studies have reported relatively high levels of PCBs in the semm or adipose tissues of occupationally-exposed individuals, eg, >3000 ppb in the semm (57,58). Not surprisingly, after these exposures were terminated, the PCB semm concentrations tended to decrease (59—61). 

Exposure Levels in Humans. Although some data on the levels of americium in human tissues exposed to natural background levels (food, water, and air) are available, few measurements have been made on the americium content in human tissues. The principal source of information about occupationally exposed individuals is the U.S. Transuranium and Uranium Registries (USTUR) Tissue Program and database, established to document levels and distribution of uranium and transuranium isotopes in human tissues for occupationally exposed workers (USTUR 1999). Several major database files are available. 

Increases in ALAS activity have been observed in lead workers (Meredith et al. 1978). Leukocyte ALAS was stimulated at a PbB level of 87 pg/dL (Meredith et al. 1978), a level at which ALAD activity is already significantly inhibited. ALAD activity correlated inversely with PbB levels in occupationally exposed individuals (Alessio et al. 1976 Wada et al. 1973), as has been seen in subjects with no occupational exposure (Secchi et al. 1974). Erythrocyte ALAD and hepatic ALAD activities were correlated directly with each other and correlated inversely with PbB levels in the range of 12-56 pg/dL (Secchi etal. 1974). 

People living near hazardous waste sites may be exposed to lead via ingestion of contaminated water or soils or by inhalation of lead particles in the air. For people not living in the vicinity of hazardous waste sites, the major route of exposure to lead is ingestion, particularly of lead-contaminated water, food, soil, lead-based paint chips, or dusts (the latter two are particularly relevant to children in lower-income urbanized populations). For occupationally exposed individuals, the predominant route of exposure is the inhalation of lead particles with oral ingestion also important in many cases. 

Mishra, K.P., Singh, V.K., Rani, R., Effect of lead exposure on the immune response of some occupationally exposed individuals, Toxicology 188, 251, 2003. 

Sarlo, K., et al., Respiratory allergenicity of detergent enzymes in the guinea pig intratracheal test association with sensitization of occupationally exposed individuals, Fundam. Appl. Toxicol., 39, 44, 1997. 

Continued researeh into the development of sensitive and specific biomarkers of exposure and effect for 3,3 -dichlorobenzidine, and the validation of these biomarkers in occupationally exposed individuals would be valuable. Since at this point there are no validated biomarkers of exposure and effect in adults, it makes sense to focus efforts on occupationally exposed adults rather than children who are unlikely to be exposed. There are no data on interactions of 3,3 -dichlorobenzidine with other chemicals in children or adults. There are no pediatric-specific methods to reduce peak absorption for 3,3 -dichlorobenzidine... 

Ashley et al. (1994) reported a mean blood level of 1,4-dichlorobenzene of 1.9 ppb (median 0.33 ppb) in 1,037 samples collected from a reference group of non-occupationally exposed individuals. Concentrations of VOCs in blood samples from a group of 126 nonsmokers and 42 smokers were also studied (Ashley et al. 1995). These authors found that mean blood levels were 3.2 ng/L (ppb) (median. 

According to the Federal Research in Progress Database, Perry and Tsao at the Lawrence Berkeley Laboratory are studying the chemical species and transport of thorium in soil. In other on-going projects, Krey et al. at Environmental Measurements Laboratory in New York are studying the daily intake of thorium, and Mclnroy et al. at Los Alamos National Laboratory are studying the tissue levels of thorium in the general population and occupationally exposed individuals. 

Higher serum nickel levels have been found in occupationally exposed individuals compared to nonexposed controls (Angerer and Lehnert 1990 Elias et al. 1989 Toijussen and Andersen 1979). Serum nickel levels were found to be higher in workers exposed to soluble nickel compounds compared to workers exposed to less-soluble nickel compounds (Toijussen and Andersen 1979). Concentrations of nickel in the plasma, urine, and hair were similar in nickel-sensitive compared to nonsensitive individuals (Spruit and Bongaarts 1977). 

This Report is one of the series developed under the auspices of Scientific Committee 46, a scientific program area committee of the National Council on Radiation Protection and Measurements (NCRP) concerned with operational radiation safety. The Report provides practical recommendations on the use of personal monitors to estimate effective dose equivalent (Hg) and effective dose (E) for occupationally-exposed individuals. The Report is limited to external exposures to low-LET radiation. Recent additions to the radiation protection literature have made the recommendations possible. In order to avoid delay in utilizing the recommendations in the United States, the quantity as well as E, has been included until such time as the federal radiation protection guidance and associated implementing regulations are revised to express dose limits in E as recommended by the NCRP. 

SC 46-2 Uranium Mining and Milling—Radiation Safety Programs SC 46-3 ALARA for Occupationally Exposed Individuals in Clinical Radiology... 

Both Pu and Th will probably enter the skeleton and other internal tissues predominantly from inhalation. This statement is based on the fact that in the field, Pu and Th demonstrate similar transfers from soil to small mammals and laboratory studies demonstrate similar metabolic characteristics (1,3,23). Soil chemical behavior is also similar (20). As demonstrated in Table I, natural Th in human bone originates largely from inhalation, even assuming that adsorption from the diet is 0.1%. Another strong agrument for the importance of inhalation is found in tissue distributions of Th-232 and Th-230 in humans. Table V summarizes work by Wrenn, et al. (53) which shows that lungs of non-occupationally exposed individuals contains burdens of Th isotopes comparable to the skeleton. Thorium-228 distributions are different from Th-230,... 

For 2,3,7,8-TCDD, the majority of the effects have been reported among occupationally exposed individuals such as producers or users of chemicals in which 2,3,7,8-TCDD might have occurred as impurities, and among residents of communities contaminated with 2,3,7,8-TCDD. Effects that have been associated with exposure to materials contaminated with 2,3,7,8-TCDD in some studies include... 

Irritating to skin, eyes, respiratory tract skin disease in occupationally exposed individuals... 

Kathren RL, Mclnroy IF, Moore RH, et al. 1989. Uranium in the tissues of an occupationally exposed individual. Health Phys 57 17-21. 

Occupationally exposed individuals have also reported muscle aches and pain, lethargy, general fatigue, and headaches following long-term exposure to carbon disulfide vapors. Ocular effects that have been observed in people exposed in occupational settings include dot hemorrhages and microaneurysms. 

The neurophysiological and neuropsychological health effects of mercury have been extensively studied in occupationally exposed individuals in an effort to monitor body levels and to determine a threshold value below which these effects are unlikely to occur. As with other biomarkers of effect, neurological changes induced by mercury may resemble exposure to other chemicals that can cause damage to the brain. 

Other than isolated studies with human microsomes (Schnellmann et al. 1983), data regarding biotransformation of PCBs in humans are limited to information about occupationally exposed individuals. 

SARLO, K CLARK, E.D., RYAN, C.R. BERNSTEIN, D.I. (1990) ELISA for human IgE antibody to subtilisin A (Alcalase) correlation with RAST and skin test results with occupationally exposed individuals. Journal of Allergy and Clinical Immunology, 86, 393-399. 

There are substantial data available on which to base conclusions regarding the potential health effects of carbon disulfide exposure in residents near hazardous waste sites and occupationally exposed individuals. The principal adverse health effects noted in humans exposed via inhalation are neurotoxic and... 

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