Metals occupational exposure values

TABLE 22.1 Occupational exposure values for various metals (ACGIH 1998) ... 

As shown in Table 5-4, the NHANES median values observed for the four metals in the U.S. population correspond, on the average, to about 4% of the BEIs, whereas the 95th percentile values reach up to over 30% of the BEI. Mercury is a special case because occupational exposures to mercury... 

SO2 is a toxic gas and exposure limit values for workers should be taken into account. The occupational exposure limit in most countries is 2 ppm (5 mg/m ) over 8 hours. Sulphur- and oxygen-containing deposits may form on the furnace wall. Under unfavourable conditions these deposits can be immersed into the molten metal where they cause reactions leading to metal eruptions from the surface. Frequent removal of scaling can prevent this from happening. 

Exposure to tantalum metal dust may cause eye injury and mucous-membrane irritation. The threshold limit value (TLV) in air is 5 mg/m, LD q is <400 mg/kg and the Occupational Safety and Health Administration (OSHA) time weighted average (TWA) exposure limit is 5 mg/m (47). The immediate dangerous to life or health (IDLH) concentration is 2500 mg/m (48). Whereas some skin injuries from tantalum have been reported, systemic industrial poisoning is apparently unknown (47). 

Analysis of metals in hair is of limited practical value for monitoring exposure to metals in occupational settings due to the very distinct possibility of hair contamination with exogenous metals present in the ambient air. 

The Occupational Safety and Health Administration permissible exposure limit (PEL) time-weighted average (TWA) for nickel metal and other nickel compounds as nickel is 1 mg m the PEL TWA for nickel carbonyl is 0.007 mg m . The ACGIH threshold limit values (TLVs) for nickel metal, insoluble compounds, soluble compounds, nickel carbonyl, and nickel subsulflde, all expressed as nickel, are 1.5, 0.2, 0.1, 0.12, and 0.1 mgm, respectively. Except for nickel carbonyl, all of the TLVs are expressed as inhalable particulate. The US EPA reference dose for soluble nickel salts is 0.02 mg kg day, but this value is undergoing reevaluation, due to the availability of several relevant new studies. 

The American Conference of Governmental Industrial Hygienists threshold limit value, 8 h time-weighted average is 0.1 mgm as inhalable fraction. The (US) Occupational Safety and Health Administration permissible exposure limit, 8 h TWA, is 1.0 mg m. The (US) National Institute for Occupational Safety and Health (NIOSH) considers nickel metal and other... 

Employees are frequently monitored when working in an environment where exposure to toxic metals is a possibility. The most common form of monitoring involves quantification of airborne concentrations of metals in the production process. Threshold limit values for airborne concentrations and time-interval exposure concentrations are defined by the U.S. National Institute for Occupational Safety and Health (NIOSH) to ensure worker safety. Workers may also be monitored by quantification of biological samples. The most common sample used is a random urine sample, and results are expressed in concentration units for the metal of interest per gram of creatinine to normalize for... 

Pellet F, Perdrix A, Vincent M and Mallion JM (1984) Biological determination of urinary cobalt. Significance in occupational medicine in the monitoring of exposures to sintered metallic carbides. Arch Mai Prof Med Trav Secur Soc 45 81-85. Perdrix A, Pellet F, Vincent M, De Gaudemaris R and Mallion JM (1983) Cobalt and sintered metal carbides. Value of the determination of cobalt as a tracer for exposure to hard metals. Toxicol Fur Res 5 233-240. 

Metallic or elemental mercury volatilizes to mercury vapor at ambient air temperatures, and most human exposure is by way of inhalation. The saturated vapor pressure at 20.0°C is 13.2mg/m. This value far exceeds the threshold limited value (TLV) of 0.05 mg/m accordingly, mercury intoxication due to inhalation of the vapor readily occurs in various occupational and environmental situations. Mercury vapor readily diffuses across the alveolar membrane and is hpid soluble so that it has an affinity for the central nervous system and red blood cells. Metallic mercury, unlike mercury vapor, is only slowly absorbed by the G1 tract (0.01%) at a rate related to the vaporization of the elemental mercury and is of negligible toxicological significance. 

People living in proximity to mining areas are often as vulnerable to Hg exposures as are those occupationally exposed to Hg. Therefore, Acosta-Saavedra et al. (2011) concluded that women and children in Mexico face Hg exposure risks for both geographical and socioeconomical conditions. For example, in a monitoring study of Hg and other toxic metals in children living in areas close to mine tailings in southern Mexico, it was found that urinary Hg was elevated (Moreno et al. 2010). The individuals of interest were 50 children whose age ranged from 6 to 11 years the results indicated that 30% of children had Hg levels above the reference value (0.7 pg L- ) for urine. 

---