Persistent toxic chemical chemicals

Kellogg, S.T., Chatterjee, D.K., and Chakrabarty, A.M., Plasmid-assisted molecular breeding New techniques for enhanced biodegradation of persistent toxic chemicals, Science, 214, 1133-1135, 1981. 

Allan, R. J. (1994). Transport and Fate of Persistent Toxic Organic Chemicals in Aquatic Ecosystems the Niagara River to St. Lawrence River Estuary Example. In Hydrological, Chemical a. Biological Processes of Transformation a. Transport of Contaminants in Aquatic Environments, Proc. of the Rostov-on-Don symposium. May 1993, IAHS Publication, 219, pp. 21-32. 

UNEP Chemicals, 2002. Regionally based assessment of persistent toxic chemicals - Indian Ocean, regional report, p. 91. 

The peril of persistent toxic chemicals was realized long after tons of these chemicals had been spread throughout the world. Once hailed as perfect chemicals for their intended uses, these long lasting OCPs, for examples, become burden to the environment and ecosystems where they have been... 

More than 30,000 different chemicals are produced or used in the Great Lakes region of the United States. This area contains 118 different hazardous waste sites that are contaminated with thousands of different chemicals. A study of this region has shown that human populations in it have elevated body burdens of persistent toxic chemical compounds. 

Many of the observed Great Lakes region toxic effects are attributed to persistent toxic chemical compounds. TCDD is associated with human thyroid hormone fluctuation, problems in male reproductive function, and neurological malfunction. Hexachlorobenzene (HCB) and methyl mercury (MeHg) are associated with human thyroid hormone fluctuation, problems in female reproductive function, neurological and neurodevelopmental problems. These effects, summarized in Table 13.1, illustrate the difficulty in attributing a particular toxic effect to a single chemical, particularly when one considers the potential impacts of thousands of other chemicals. 

Table 13.1 Toxic Effects of Persistent Toxic Chemical Compounds1541...

Liability for possession and production of persistent toxic chemicals, particularly PCDD and PCDF is going to increase. In Ontario the recent promulgation of the "Spills Bill" has placed the liability for immediate cleanup and damages for a spill of toxic chemicals directly on the transporter and producer. This bill will eventually increase the cost of transportation of waste and promote on-site destruction devices. 

Measurement of exposure can be made by determining levels of toxic chemicals in human serum or tissue if the chemicals of concern persist in tissue or if the exposure is recent. For most situations, neither of these conditions is met. As a result, most assessments of exposure depend primarily on chemical measurements in environmental media coupled with semi-quantitative assessments of environmental pathways. However, when measurements in human tissue are possible, valuable exposure information can be obtained, subject to the same limitations cited above for environmental measurement methodology. Interpretation of tissue concentration data is dependent on knowledge of the absorption, excretion, metabolism, and tissue specificity characteristics for the chemical under study. The toxic hazard posed by a particular chemical will depend critically upon the concentration achieved at particular target organ sites. This, in turn, depends upon rates of absorption, transport, and metabolic alteration. Metabolic alterations can involve either partial inactivation of toxic material or conversion to chemicals with increased or differing toxic properties. 

US EPA (2007) Fact Sheet L Multimedia Strategy for Priority Persistent, Bioaccumulative, and Toxic (PBT) Chemicals. [Online - accessed 1 May 2007] Available from URL http //www.epa.gov/ pbt/pubs/fact.htm... 

Van Voris P, Cataldo DA, Ligotke MW, et al. 1987. Acute environmental toxicity and persistence of selected chemical agent simulants diisopropyl flourophosphate (DFP) and diisopropyl methylphosphonate (DIMP). NTIS No. AD-A181-309. 

Reducing the presence of the most persistent, bioaccumulative, and toxic (PBT) chemicals in hazardous wastes by 50% by the year 2005. 

Witzmann FA et al. Toxicity of chemical mixtures proteomic analysis of persisting liver and kidney protein alterations induced by repeated exposure of rats to... 

USEPA (2008) Persistent bioaccumulative and toxic (PBT) Chemical Program. DDT. United States Environmental Protection Agency. Available from www.epa.gov... 

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. 

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