Levels in the environment

Butyl benzyl phthalate 1 and 20 ng/m Mean concentrations in office (4) 

Concentrations of di-n-butyl phthalate dissolved in precipitation have ranged from 3 to 496 ng/L, and di-(2-ethylhexyl) phthalate has been detected from 1.6 to 429 ng/L. Thuren and Larsson concluded that di-n-butyl phthalate and di-(2-ethylhexyl) phthalate were widely distributed in the atmosphere in Sweden, and that there appeared to be no specific sources or patterns for their distribution. 

Plasticizers have been detected in surface water (Table 18.4) at concentrations ranging from 0.002 to 86 pg/L, and in groundwater samples at concentrations of 8 ng/L to 200 pg/L (Table 18.5). Kohli et al generalized that the most commonly occurring phthalates in siuface water were di-(2-ethylhexyl) phthalate and di-n-butyl phthalate. However, some of the samples in these reports were biased in that the samples were collected from monitoring wells near waste sites and industrial areas. Plasticizers have also been reported in samples of drinking water (Table 18.6) at concentrations ranging from 0.03 to 470 pg/L (see HSDB for specific information on the location of the samples and frequency of 

Butyl benzyl phthalate 0.06 to 2.4 pg/L Mississippi River (USA), Rhine (Netherlands) (5) 

Di-n-butyl phthalate 0.20 to 42 pg/L Various rivers (USA, Europe, Japan) Urban runoff (5,10) 

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This reduction in energy use can be achieved without affecting the required pollution levels in the environment by the improved collection methods that arc covered in these guides,... 

For the octyltin compounds, the only source of these substances relates to their use as stabilizer compounds in PVC products (including other relevant life cycle stages such as production). Thus, it can be safely assumed that measured levels in the environment relate to this application. 

Overall, there is only weak evidence to suggest that levels in the environment to which the general population is exposed could induce adverse endocrine effects. 

Both PCDDs and PCDEs are refractory lipophilic pollutants formed by the interaction of chlorophenols. They enter the environment as a consequence of their presence as impurities in pesticides, following certain industrial accidents, in effluents from pulp mills, and because of the incomplete combustion of PCB residues in furnaces. Although present at very low levels in the environment, some of them (e.g., 2,3,7,8-TCDD) are highly toxic and undergo biomagnification in food chains. 

Public concern about PBDE levels in the environment was heightened when it was shown that a sharp increase in the concentration of certain PBDEs had occurred in human breast milk over only a 10-year period (Meironyte et al. 1999 Noren and Meironyte 2000), and the levels of exposure in some infants and toddlers were similar to those shown to cause developmental neurotoxicity in animal experiments (Costa and Giordano 2007). As a result of these concerns, the majority of commercial PBDE mixtures have been banned from manufacture, sale, and use within the European Union. 

In addition to high sensitivity, a requirement for any acceptable analytical method is high specificity because at very low levels few confirmatory procedures can be used to establish the identity of a particular compound. A method which uniquely combines high sensitivity with high specificity is high resolution mass spectrometry. We have used this method as the basis for an approach which we believe will make possible a meaningful assessment of TCDD levels in the environment. 

Tetracyclines are broad-spectrum antibiotics with activity against Gram-positive and Gram-negative bacteria that have been widely used for the treatment of infectious diseases in veterinary and human medicine, as well as additives in animal foodstuffs. Normally tetracyclines are not found at high levels in the environment because they readily precipitate with cations such as calcium and are accumulated in sewage sludge or sediments [3,20,26]. 

Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs), in contrast to other chlorinated chemicals, have never been commercially manufactured nor are of any benefit or known use. PCDD/Fs are ubiquitous contaminants, which are released as byproducts of incomplete combustion or as impurities in chemical processes, and that their levels in the environment are increasing. 

Exposure Levels in Humans. The database for -hexane exposure levels in humans is limited to a few older detections of -hexane in breast milk and determinations of levels in body fluids and alveolar air collected in foreign countries. A more current and complete database would be helpful in determining the current exposure levels, thereby permitting the estimation of the average daily dose associated with various scenarios (e.g., living near a hazardous waste site). Since -hexane is rapidly metabolized within the human body, further studies correlating levels in the environment with the levels of metabolites and biomarkers in humans would be helpful. This information is necessary for assessing the need to conduct health studies on these populations. 

Methods for Determining Biomarkers of Exposure and Effect. Besides environmental exposure, exposure to cyanide can also occur from consumption of cyanide-containing food, metabolism of certain drugs, and smoking cigarettes. Since so many factors can influence cyanide exposure, the exact correlation between cyanide concentrations in the body and its level in the environment has not been made. Therefore, measuring cyanide and/or thiocyanate levels in blood and urine cannot be used as a biomarker for exposure to low cyanide concentrations. Analytical methods of required sensitivity and reliability to detect cyanide and thiocyanate in blood, plasma, and urine of both unexposed and exposed persons are available (see Table 6-1 and Table 6-3). Further studies determining biomarkers for exposure to low cyanide concentrations would be useful. 

Although we can measure the amount of chloroform in the air that you breathe out, and in blood, urine, and body tissues, we have no reliable test to determine how much chloroform you have been exposed to or whether you will experience any harmful health effects. The measurement of chloroform in body fluids and tissues may help to determine if you have come into contact with large amounts of chloroform. However, these tests are useful only a short time after you are exposed to chloroform because it leaves the body quickly. Because it is a breakdown product of other chemicals (chlorinated hydrocarbons), chloroform in your body might also indicate that you have come into contact with those other chemicals. Therefore, small amounts of chloroform in the body may indicate exposure to these other chemicals and may not indicate low chloroform levels in the environment. From blood tests to determine the amount of liver enzymes, we can tell whether the liver has been damaged, but we cannot tell whether the liver damage was caused by chloroform. 

The Statistical Model. The residue levels of the individual specimens in a particular subpopulation (e.g., a given Census Division and age, sex, race category) are assumed to follow a lognormal distribution. Previous studies on NHATS data have found the lognormal distribution to be appropriate and goodness of fit tests performed on the collected data verified that the assumption is still reasonable. The lognormal model assumes only non-negative values and allows the variances of the different subpopulation distributions to increase with the mean levels. This distribution is commonly used to model pollutant levels in the environment. 

Thirty years after bans on many toxic organic chemicals first went into effect, their levels in the environment in many developed countries had decreased substantially. For example, health scientists and environmentalists now believe that concentrations of DDT remaining in soils and water in the United States are so low as to pose no threat to human health or to the health of other animals. 

Nickel normally occurs at very low levels in the environment, and therefore, very sensitive methods are needed to detect nickel in most environmental samples. You may be exposed to nickel by breathing air, drinking water, eating food, or smoking tobacco containing nickel. 

LEVELS IN THE ENVIRONMENT ASSOCIATED WITH LEVELS IN HUMAN TISSUES AND/OR HEALTH EFFECTS... 

Thus, structure-activity relationships developed to estimate levels in biological media based on the partitioning properties of a chemical may not provide accurate information for isophorone. Furthermore, only one bioaccumulation study was available. In this study, which indicated a low potential for bioaccumulation, fish were exposed to isophorone in water rather than in food. From these data, it appears that food chain bioaccumulation may be occurring, and a clearer understanding of the potential for this would aid in determining how levels in the environment affect the food chain and potentially impact on human exposure levels. 

If there is only some degree of degradation or if the rate of degradation is slow compared with the rate of input, the parent compounds will be present at constant levels in the environment provided that the input rate is higher than their rate of degradation or mineralization (pseudo-persistence or second-order persistence). 

The success of stabilized phosphate programs, but mixed with growing concerns over phosphate levels in the environment, has resulted in the development of many programs with lower PO4 content but blended with various combinations of zinc, phosphonate, and polymers. 

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