Level of Concern

Accepts data input for the level of concern Uses the data entered to calculate the vulnerable... 

EPA must first make determinations about which contaminants to regulate. These determinations are based on health risks and the likelihood that the contaminant occurs in public water systems at levels of concern. The National Drinking Water Contaminant Candidate List (CCL), published March 2, 1998, lists contaminants that (1) are not already regulated under SDWA (2) may have adverse health effects (3) are known or anticipated to occur in public water systems and (4) may require regulations under SDWA. Contaminants on the CCL are divided into priorities for regulation, health research and occurrence data collection. 

If the exposure level (E) exceeds tliis tlireshold (i.e., E/RfD exceeds unity), tliere may be concern for potential noncancer effects. As a rule, tlie greater tlie value of E/RfD above unity, tlie greater tlie level of concern. However, one should not interpret ratios of E/RfD as statistical probabilities a ratio of 0.001 does not mean tliat tliere is a one in one tliousand cliance of the effect occurring. Furtlier, it is important to empliasize tliat tlie level of concern does not increase linearly as tlie RfD is approached or exceeded because RfDs do not have equal accuracy or precision and are not based on tlie same severity of toxic effects. Thus, tlie slopes of the dose-response curv e in excess of the RfD can range widely depending on tlie substance. 

There are several limitations to tliis approach that must be acknowledged. As mentioned earlier, tlie level of concern does not increase linearly as the reference dose is approached or exceeded because the RfDs do not luive equal accuracy or precision and are not based on the same severity of effects. Moreover, luizm-d quotients are combined for substances with RfDs based on critical effects of vaiy ing toxicological significance. Also, it will often be the case that RfDs of varying levels of confidence Uiat include different uncertainty adjustments and modifying factors will be combined (c.g., extrapolation from animals to hmnans, from LOAELs to NOAELs, or from one exposure duration to anoUier). 

The potential for noncarcinogcnic health effects is evaluated by comparing iui exposure level over a specified lime period (c.g., lifetime) with a reference dose derived for a similar exposure period. The ratio of exposure to toxicity in called a liazard quotient and, when it is greater tlien unity tlierc is a higher level of concern for potential noncancer effects. 

T/ e effect of altering major assumptions on the downwind distance (radius) of the estimated vulnerable zone. Calculations made using (1) credible worst case assumptions for initial screening zone. (2) reevaluation and adjustment of quantity released and/or rate rf release cf chemical, (3) reevaluation and adjustment of wind speed (increase) and air stability (decrease), (4) selection of a higher level of concern. Note that adjustment oftwo or more variables can have an additive effect on reducing the size cf the estimated vulnerable zone. 

Note also that the relative sizes cf the altered zones are not to scale (e.g., choosing a higher value for the level of concern does not always result in a smaller zone than the use of greater wind speed and less atmospheric stability). 

Define the levels of concern - high, moderate, and low - for each hazard. 

All of the hazard and benchmark criteria developed for the Green Screen are presented in the report, along with information on government and other precedents for classification that were used to help establish the thresholds. The hst of hazard categories and threshold values used to define levels of concern in the Green Screen are presented in Table 8.1. 

Studies carried out by the Center for Disease Control and Prevention (CDC) show that the levels of lead in the blood of U.S. children have been getting lower and lower. This is because lead is banned from gasoline, residential paint, and solder that is used for food cans and water pipes. Still, about 900,000 U.S. children between the ages of 1 and 5 years are believed to have blood lead levels equal or greater than 10 ig/dL, the CDC level of concern. 

It does not contain a probabilistic modeling component that simulates variability therefore, it is not used to predict PbB probability distributions in exposed populations. Accordingly, the current version will not predict the probability that children exposed to lead in environmental media will have PbB concentrations exceeding a health-based level of concern (e.g., 10 pg/dL). Efforts are currently underway to explore applications of stochastic modeling methodologies to investigate variability in both exposure and biokinetic variables that will yield estimates of distributions of lead concentrations in blood, bone, and other tissues. 

OSHA Blood lead level of concern (all occupations including the construction industry) 40 pg/dL... 

The weight of evidence suggests that PbB levels of "10-15 g/dL and possibly lower" are the levels of concern (ATSDR 1993 Davis 1990 EPA 1986). The Department of Health and Human Services (DHHS) has determined that primary prevention activities should begin at blood lead levels of 10 g/dL in children (CDC 1991). 

Atmospheric Dispersion Models Atmospheric dispersion models generally fall into the categories discussed below. Regardless of the modeling approach, models should be verified that the appropriate physical phenomena are being modeled and validated by comparison with relevant data (at field and laboratory scale). The choice of modeling techniques may be influenced by the expected distance to the level of concern. 

Information on current levels of endrin in the environment is limited however, the available data indicate that concentrations in all environmental media are generally negligible or below levels of concern. The FDA has concluded that endrin is no longer present in the environment to the extent that it may be contaminating food or feed at levels of regulatory concern (USDA 1995). No information could be found in the available literature on levels of endrin aldehyde or endrin ketone in the environment. 

Tables 1-1, 1-2, 1-3, and 1-4 show how little we know about the levels of 1,2-diphenylhydrazine that might affect your health. As is shown in Table 1-4, animals that ate food containing 1,2-diphenylhydrazine for a long time developed lung inflammation, stomach damage, and liver damage, and some died. Although the levels of exposure that cause harmful effects in humans are not known, as discussed in Section 1.2, 1,2-diphenylhydrazine is not likely to be found in food, and you are not even likely to be exposed to levels of concern if you live near a hazardous waste site. Additional information on levels of exposure associated with effects can he found in Chapter 2.

It is obvious that such an assessment is formidable, technically difficult, and extremely expensive. Since an environmental source assessment study is required to characterize the total pollution potential of all waste streams, the sampling program must be more extensive than those conducted for the acquisition of process or control engineering data. Assessment sampling is more complete in that all waste streams are sampled and no attempt is made to limit sampling to a preselected number of process streams. The sampling is also more comprehensive in that all substances of potential environmental concern must be detectable above some minimum level of concern. These requiements of completeness and comprehensiveness call for a strategy of approach in which the philosophy and structure ensure maximum utilization of available resources. 

The FDA allows women to enter carefully controlled and monitored trials in which adequate contraceptive measures and pregnancy testing are performed without requiring results from animal reproductive toxicity tests. In Japan and Europe, because of the high level of concern regarding imintentional exposure of the developing embryo or foetus, an assessment of fertility in a rodent, and embryo/foetal development in a rodent or non-rodent are required if women of childbearing potential are to be included in a Phase I trial. The FDA would expect such results to support Phase II and Phase III studies. 

Lead is one of the most intensively studied hazardous compounds of the twentieth century. The more toxicologists and other researchers investigated the health effects of lead, the more they realized that even very low levels of lead exposure were hazardous. The most common biomarker of lead exposure is the blood lead level, usually measured in micrograms (jig) per one hundredth of a liter of blood (dl) or jlg/dl. For example, many regulatory agencies set 40 jlg/dl as a level of concern for adult male workers. Typically, at this level workers would be removed from the environment responsible for the exposure and ideally some determination would be made as to the cause of the exposure. The blood level of concern for children has dropped steadily, as shown in Figure 7.1. 

Safety or uncertainty factors are often applied at the end of an assessment, for example, as a level of concern to which a risk quotient or toxicity-exposure ratio is compared. 

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