Uranium occupational limits

EPA has also decided that any accidental uranium waste containing 0.1 curies of radioactivity (150 kilograms) must be cleaned up. EPA calls this the Reportable Quantity Accidental Release. EPA also has established a standard for uranium mill tailings, hi the workplace, NIOSH/OSHA has set a Recommended Exposure Limit (REL) and a Permissible Exposure Limit (PEL) of 0.05 mg/m (34 pCi/m ) for uranium dust, while the NRC has an occupational limit of 0.2 mg/m (130 pCi/m ). The NRC has set uranium release limits at 0.06 pCi/m (0.09 pg/m ) of air and 300 pCi/liter (450 pg/liter) of water. NRC and OSHA expect that the public will normally be exposed to much lower concentrations. For more information about recommendations the federal government has made to protect your health, see Chapter 7. 

The occupational limits for thorium, uranium and some critical decay products are listed in Table 26.1-2. For the chemotoxicity limit of uranium, American and German values for different exposure situations are given. Due to the dominance of the radiotoxicity in the case of thorium, permissible concentration limits are generally based only on the radioactivity. However, former Eastern bloc countries have set a threshold limit for thorium in workroom air (ILO 1980). The annual limit of intake (ALI) will result... 

The occupational exposure values for the inhalation of uranium have been compiled by the American Conference of Governmental Industrial Hygienists (ACGIH) [14]. These are air concentration exposure limits based on the chemical effects of uranium. In contrast, the International Commission on Radiological Protection (ICRP) has developed the annual limit on intake (ALI) for ingestion and inhalation of uranium compounds based solely on the radiation doses received by tissues and organs of the body [12,15]. Whether the primary concern is the chemical toxicity or radiation dose, the occupational limits take the solubility of the uranium compound into consideration. The occupational limits are summarized in Table 3. It must be emphasized that the air concentration exposure limits are for the typical 8-hr day (see Abbrevi-... 

TABLE 3. Occupational Limits for Air Concentration Exposure to Uranium [14]... 

Table 2-8 shows the mass equivalents for natural and depleted uranium for radiation levels that caused potential radiological effects in rats exposed once for 100 minutes to airborne 92.8% enriched uranium with an estimated specific activity of 51.6 pCi/g (Morris et al. 1989). These mass equivalent values for natural and depleted uranium for the minimal concentration of radioactivity that is expected to induce potential radiological effects are well above levels that would be expected to be inhaled or ingested. In addition, the mass equivalents for natural and depleted uranium for potential radiological effects are 3,600 and 76,500 times higher, respectively, than the occupational exposure limits (short-term exposure) recommended by the National Institute for Occupational Safety and Health (NIOSH 1997). Therefore, MRLs for uranium based on studies that used enriched uranium are inappropriate. 

The purpose of this chapter is to describe the analytical methods that are available for detecting and/or measuring and monitoring uranium in environmental media and in biological samples. The intent is not to provide an exhaustive list of analytical methods that could be used to detect and quantify uranium. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used to detect uranium in environmental samples are the methods approved by federal agencies such as EPA, DOE, and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by a trade association such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that refine previously used methods to lower detection limits, and/or to improve accuracy and precision. 

Tab. 26.1-2 Critical effects and occupational exposure limits for thorium, different exposure pathways uranium and decay products for ...

As with some of the chronic animal studies, exposures in most of the occupational miner cohorts consist of exposure to radon and radon progeny in the presence of other contaminants such as uranium ore dust, diesel-engine exhaust, or other mine pollutants. Only a few studies of lung cancer associated with environmental exposures to radon and radon daughters have been reported. These studies are primarily case-control or case-referent studies that involve a small number of subjects and have exposure estimates that are based on either surrogates for measurements or limited measurements. Additional studies of the extent of the hazard associated with environmental radon daughter exposures would provide useful information since radon is an ubiquitous substance, especially as they compare to estimates of the human health hazard based on the occupational setting. 

Workers who mine and process mineral sands containing tin and associated trace metals can also be exposed to uranium and thorium dusts from the sands (252). In a United Nations-sponsored study of radiological exposures in the tin by-product industry in Southeast Asia, Hewson found that many of these exposures are above occupational exposure limits, but could easily be reduced by use of standard radiation protection practices involving ventilation and respiratory protection. Implementation of such practices may be difficult, however, because most of the estimated 2000 workers employed in this indnstry work in plants that employ fewer than 20 workers, with many plants employing fewer than 5 workers. 

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