Environmental standards exposures

Laxen DP, Raab GM, Fulton M. 1987. Children s blood lead and exposure to lead in household dust and water—a basis for an environmental standard for lead in dust. Sci Total Environ 66 235-244. 

Fig. 8.1 Dose-response curve showing log dose on the X-axis and percent response (Effect) on the Y-axis. The figure illustrates the location of regulatory values such as the NOEL, Occupational Exposure Levels (OELs) or environmental standards such as Acceptable Daily Intake (ADI)...

Regulators use DNEL and PNEC to set health or environmental standards, but usually in conjunction only with exposure levels. For non-threshold effects, when a DNEL or PNEC may not apply, probabilities of the incidence of an effect for an individual within a population are used to set regulatory limits on exposure. Recent regulatory discussions within the REACH Implementation Projects... 

The endpoint of both EUSES and USES is a quantitative comparison per substance of the results of the effects and the exposure assessment. The latter aims at providing reasonable-worst-case results by applying unfavorable, but not unrealistic, standard exposure scenarios. The risk assessment is carried out in a stepwise procedure, starting with data input aud estimation, and further involving estimation of emissions, prediction of environmental distribution, calculation of human and environmental exposure, derivation of no-effect levels and risk... 

Despite the fact that a number of studies on the influence of environmental Cd exposure on the mortality of inhabitants of Cd-polluted areas have been conducted, to date no consensus has been achieved. Shigematsu et al. investigated the outcome of residents of Cd-polluted areas in Akita, Miyagi, Nagasaki, and Toyama Prefectures and reported lower standardized mortality rates in these polluted areas as compared to non-polluted areas with even greater decreases in the standardized mortality ratios in the most severely polluted areas [107]. 

The primitiveness of methodology echoes the lack of a clear theory of carcinogenesis. However, the gaps in knowledge and the uncertainties in methods do not constitute sufficient justification for abandoning efforts to provide the public with plausible upper bounds for cancer risks due to environmental chemical exposures. For a large number of such exposures, these estimates will necessarily be based on animal data. When quantified human exposure data are available and are related to cancer risk, these data can be useful either as a basis for extrapolation or as a standard for assessing the plausibility of risk estimates based on animal data alone."... 

Applicable target risk limits (TR) for health protection can be matched to levels specified by the environmental regulatory authority. Toxicological parameters for each contaminant can be determined from published references, such as the U S. EPA Integrated Risk Information System (IRIS). Exposure rates correspond to the chronic rate of contact or intake of the affected exposure medium (air, water, soil) by the receptor under anticipated land use conditions. As a conservative measure, these rates can be estimated based on standard exposure factors published by the regulatory authority or other source (e.g., American Industrial Health Council) for the anticipated land use at the site (e.g., residential, commercial, etc.). 

Regulatory policy for limitation of exposures through environmental standards, etc. 

Once EPA has determined that a given requirement (e.g., labeling) meets this standard, there would be a presumption that more drastic requirements (e.g., a ban on production) would be unduly burdensome and therefore unnecessary to control the chemical s risks. At the very least, a burden would now be on the Agency to show that its initial evaluation of the relative costs and benefits of regulatory action was erroneous, and more severe restrictions on the chemical are in fact necessary. To make this showing, EPA would need to conduct a full reanalysis of the evidence concerning the chemical s health and environmental effects, exposure patterns, uses and benefits. 

Recently, EPA issued its environmental standards for the potential waste repository at Yucca Mountain, Nevada. Iodine-129 is one of the more important radionuclides of concern in the large inventory of spent reactor fuel and defense high-level waste. This standard limits the radiation exposure of individuals, and radionuclide concentrations in ground water from the release of I-129 and other radionuclides in the vicinity of Yucca Mountain. 

Another reason for a large amount of monitoring is to establish a baseline of exposure. Environmental standards requiring time-weighted-average calculations require monitoring for a specified time period. Some standards also require monitoring at specified time intervals. 

Stricter environmental standards and improved protective measures have reduced the level of exposure of workers in the chlor-alkali industry. In the 1960s, the mean level of mercury in the urine of Swedish mercury-cell workers was 100-140 irgL" and the peak level 300p,gL In 1990, the mean value was 30p,gL and the peak value 120 [36]. 

The main sources of government environmental standards are OSHA and EPA. OSHA sets workplace standards. NIOSH makes recommendations on exposure Umits and compiles related helpfid information. EPA sets standards for air and water quality for the general pubUc. Other agencies, like CPSC and PDA, also set reference standards related to certain products. Por work environments, the American Conference of Governmental Industrial Hygienists... 

Decoy materials of this composition undergo the above reaction to reach temperatures of 820°C in less than one second and above 750°C for twelve secrmds after their exposure to air. Presently this type of material is used in a commercial decoy flare that is composed of pyrophoric iron coated onto steel foil articles [35]. Due to increasingly demanding materials performance, environmental standards, aging, and duty-cycle, there exists a need for continued development of new materials and approaches to achieve pyrophoric materials with tailorable output. 

Clearly, poorly maintained plants and lackadaisical working practices are likely to contribute to increased risk of preventable skin disease [11]. Improperly maintained filter and ventilation systems and ill-fitting furnace exhaust pipes may increase the risk of exposure to many chemical and radiation hazards, and the standard clean room ventilation systems will re-circulate solvent vapours if these are not properly expelled [11, 24]. Such situations may arise in developing countries where there is often an absence of regulations regarding health and environmental standards [25]. 

The importance of toxic elements in environmental chemistry is rarely questioned, but a relatively small number of elements (mercury, lead, and cadmium) have received a large share of researchers attention. The environmental chemistry of the transition metals, e.g., chromium, nickel, manganese, cobalt, copper, etc., has also been investigated principally because of their roles in metabolism, especially enzymatic processes. However, two non-metals, arsenic and selenium, and two metals, beryllium and vanadium, are elements which will become more significant in the future from environmental and toxicological points of view. Arsenic and selenium have been investigated, but much more work is needed because of the importance of these two elements in the environment. The author considers beryllium and vanadium to be problem metals of the future . The primary exposure route for both beryllium and vanadium is via the atmosphere and as lower environmental standards are imposed, more uses are found for each element, and more fossil fuels (source of V) are burned, the amounts added to the atmosphere will have more significance. 

Standard deviations from two to five or more. This means that the upper seventeenth percentile may be as much as from two to five times the mean. This variabihty is compounded by the problem of estimating the exposure of a group of workers having differing exposures to find the most exposed workers. Compared to this environmental variabihty, the variabihty introduced by the sampling and analytical error is smah, even for those methods such as asbestos counting, which are relatively imprecise. 

Health, Safety, and Environmental Factors. Sulfur dioxide has only a moderate acute toxicity (183). The lowest pubHshed human lethal concentration is 1000 ppm for 10 months. The lowest pubHshed human toxic concentration by inhalation is 3 ppm for 5 days or 12 ppm for 1 hour. The lowest pubHshed human lethal concentration is 3000 ppm for 5 months. In solution (as sulfurous acid), the lowest pubHshed toxic dose is 500 flg/kg causing gastrointestinal disturbances. Considerable data is available by other modes of exposure and to other species NIOSH standards are a time-weighted average of 2 ppm and a short-term exposure limit of 5 ppm (183). 

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