Environment persistent chemicals

Mackay D, Paterson S, Joy M (1983) Application of fugacity models to the estimation of chemical distribution and persistence in the environment. In Swann Eschenroeder (eds) Fate of chemicals in the environment. American Chemical Society Symposium Series 225 175-196... 

Because PCDD/Fs became to be recognized as the most hazardous for the environment and human beings, very restricted emission limits were introduced in the most countries. But only a few countries limits are also pursuit for PCDD/F levels in sewage sludge, however sludge is one of the ultimate sinks for persistent chemicals. 

It is briefly reported that flame retardants were among the chemicals discovered in the blood of Margot Wallstrom, European Commissioner for the Environment. Wallstrom submitted a sample for testing to illustrate the presence of persistent chemicals in the human body. The Department of Environmental Sciences at Lancaster University tested for the presence of 77 man-made chemicals. The laboratory discovered 28 chemicals in Wallstrom s blood, including polybrominated diphenyl ethers, commonly used as flame retardants. 

The chlorinated chemicals assessed do not have the same risk profile. For the more volatile chemicals the safety margins between the actual exposure and the level at which no effect on the environment would be expected is quite high. For more persistent chemicals there is a need to look to the environmental compartment where they can be accumulated (mainly in sediments and biota). For some of these chemicals the safety margin is quite low and in worst-case situations serious effects may occur. For the very persistent, bioaccumulative and toxic chemicals (like dioxins, PCBs and DDT), acceptable environmental concentrations are so low and difficult to control that the industry is committed to reducing as far as possible releases to the environment through application of Best Available Techniques (BAT), mainly with respect to dioxins. For other chemicals (PCBs, DDT), production has already been halted for some years. 

Cote MG, Plaa GL, Valli VE, et al. 1985. Subchronic effects of a mixture of persistent chemicals found in the Great Lakes. Bull Environ Contam Toxicol 34(2) 285-290. 

It turns out that most of these compounds have similar characteristics that contribute to their toxicity to both humans and other species of plants and animals. First, the compounds are environmentally persistent. Many of the early pesticides, and certainly the metals, do not break down in the environment or do so only very slowly. If persistent chemicals are released continually to the environment, the levels tend to rise ever higher. This means they are available to cause harm to other organisms, often not even the target of the pesticide. Second, the early pesticides were broad acting and toxic to many species, not just the target species. These poisons often killed beneficial insects or plants. Third, many of these compounds would bioaccumulate or concentrate in species as they moved up the food chain. The chlorinated pesticides accumulate in the fat of animals. Animals that consumed other animals accumulated more and more of these pesticides. Most species could not metabolize or break down the compounds. Lead accumulates in bone and methyl mercury in muscle. And finally, because of their persistence in the environment and accumulation in various species, the persistent toxicants spread around the world even to places that never used them. Animals at the top of the food chain, such as polar bears and beluga whales, routinely have fat PCB levels greater that 6 ppm. 

Probably the greatest concern in the workplaces is solvent exposure from cleaning agents or chemical processes. Farmers and pesticide workers can also be exposed to compounds clearly designed to affect the nervous system. The outdoor environment can contain elevated levels of a number of persistent chemicals that can adversely affect the nervous system, such as lead, mercury, and chlorinated pesticides. 

Toxaphene, or polychlorocamphene (CioHioCls), is a pesticide for cotton. It has no significant biodegradation or photolysis reactions in the environment, so it is a persistent chemical. Henry s law constant for toxaphene is Ht = 6.0 x 10 atm m /mole. The initial conditions are given in Figure E8.5.1. 

If bacteria can metabolize a chemical, this will mean that the chemical will not persist in an environment where those bacteria are present. Thus it can be expected that some currently persistent chemicals will become less persistent over time. However, such bacteria are likely to evolve only where the persistent chemical is present at particularly high concentrations. There is no reason to think that bacteria able to degrade a chemical will be available to do so wherever that chemical is present at concentrations sufficient for it to affect biological organisms. 

Niemi, G.J. et al., Structure features associated with degradable and persistent chemicals, Environ. Tox. Chem., 6, 515, 1987. 

UNEP Chemicals, United Nations Environment Programme Chemicals, 2002. Regionally based assessment of persistent toxic substances, Central and North East Asia Regional Report. December, 2002. 

Jobling S, Reynolds T, White R, et al. 1995. A variety of environmentally persistent chemicals, including some phthalate plasticizers, are weakly estrogenic. Environ Health Perspect 103 582-587. 

The toxicity associated with polychlorinated hydrocarbons, including polychlorinated naphthalenes were recognized very early due to a variety of industrial accidents.75 However, the first evidences of bioaccumulation and toxicity on animals was noted in 1966 when emaciated seabird corpses with very high PCB body burdens washed up on beaches.74 Concern over the toxicity and persistence (chemical stability) of PCBs in the environment led the United States Congress to ban their domestic production in 1977, although some use continues in closed systems such as capacitors and transformers. PCBs are persistent organic pollutants and despite the production ban in the 1970s, they still persist in the environment and remain a focus of attention.76 Their use as fire retardants was discontinued when their toxicity was discovered. 

Pohl HR, McClure P, De Rosa CT. 2004. Persistent chemicals found in breast milk and their possible interactions. Environ Toxicol Pharmacol 18 259-266. 

PEL Permissible exposure limit a legal limit set by OSHA on the length of time industrial workers may be exposed to a substance during an 8-hour time-weighted average day without adverse effects Persistence The quality of remaining for a long period of time (such as in the environment or the body). Persistent chemical substances—for example, DDT and PCBs, are not easily broken down... 

Paasivirta, J. (1992) Predicted and observed fate of selected persistent chemicals in the environment. Organohalogen Compounds 1, 367-375. 

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