Chlorinated pesticides accumulation

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. 

Soils may also become contaminated with industrial pollutants or with agricultural chemicals. For example, fields located close to industrial plants such as incinerators or metal smelters can gradually accumulate residues of combustion products and other chemicals from the fall-out from smoke plumes. Organo-chlorine pesticides, which are now largely banned, can persist in soils for many years and nitrates used in fertilisers can accumulate in soils which, under certain growth conditions, can result in high levels in certain crops. 

Bacteria, algae, and diatoms that accumulate on the coarse sand layer of the filter bed metabolize nutrients, etc., from the supply, thereby removing them. Among the benefits of slow filtration is removal of up to 50% of any chlorinated pesticide content of the influent water [6]. Slow filtration may require a prior aeration step to ensure that the biochemical processes remain aerobic, since anaerobic operation can form sulfides and amines from sulfate and nitrate, which would contribute bad odors or tastes to the supply. 

For analyzing water pollution it is necessary to know the area where the sample(s) were harvested. Among the primary water pollutants are pesticides, since they are slowly degraded and require dissemination. The chlorinated pesticides are lipophilic and are slowly accumulated in animals. The effect is due to metabolic system perturbation. Other water pollution sources are heavy metals, which are determined by the highly sensitive and selective analytical method ICP-AES.29 The sampling process, in this case, consists of chromatographic separation techniques for pesticide separation.30... 

Being at the end of the food chain, carnivorous marine mammals accumulate in their blubber chlorinated pesticides of anthropic origin, especially DDT, chlordanes, PCBs (polychlorinated biphenyls) and heptachlor, at concentrations that may be toxic to the animals. The lipid and chlorinated pesticide compositions are related to the diet the diet may be deduced, at least in part, from the detailed composition of the blubber. This approach to the biochemistry of marine mammals has produced a great number of publications, the most recent of which include the following Maruya and Lee (1998) Aguilar, Borrell, and Pastor (1999) Kannan et al. (2000) Ross et al. (2000) Watanabe et al. (2000) Kajiwara et al. (2001) Kubota, Kunito, andTanabe (2001) Le Boeuf et al. (2002) Hoekstra et al. (2003) Vetter, Jun, and Althoff (2003) Hansen et al. 

The undesirable effects of chlorinated pesticides and PCB are closely associated with their tendency to accumulate in the fatty tissues of animals, where they are found at concentrations rising to hundred of parts per million. By contrast, the concentrations reported for the C1-C2 chlorocarbons are of the order of a few parts per billion which is three to five orders of magnitude lower [43]. The significant compounds (Table 7) are chloroform and carbon tetrachloride, trichloroethylene, perchloroethylene and methyl chloroform. Methyl chloride, methylene chloride and ethylene dichloride were not detected but the analytical method used did not resolve lower MW compounds while traces of hexachloro-butadiene were found in some marine organisms from an area known to receive industrial effluents. The compounds found in the animals were also found in a few samples of marine algae but at the time of sampling, the analytical method for methyl chloride was not adequate to show its presence. 

Biological Impact of Pesticides in the Environment. Proc. Symp. Aug 18-20, 1969 Oregon State Univ., Corvallis, OR. James W. Gillett (Ed.), Environmental Health Sciences Series No. 1. Oregon State U. Press, Corvallis (1970) 6 parts I. Transport and Accumulation, 26p. II. Impact of Chlorinated Hydrocarbons on Birds, 38p. III. Banquet Session 1 D.G. Crosby, "Chemical Ecology and Man" pp.75 ... 

The long range or indirect effects have been most disturbing. The most widely used pesticides, the chlorinated hydrocarbons, are concentrated by living matter in the aquatic environment. An increasing buildup of the pesticide may occur in each link of the food chain. These effects may not be discovered for some time after initial contact, particularly if acute toxicity of the pesticide is low. Multiple contacts may increase the amount of the chemical accumulating in the animal tissues over the years. The amounts tolerated before noticeable effects vary with the particular animal species and the pesticide. Some species can tolerate larger amounts, but sooner or later are affected by decreased fertility, interference with normal food sources, and eventually death (29). The oyster is particularly efficient in its ability to concentrate chlorinated hydrocarbon pesticides. After seven days in water at 10 p.p.b. of DDT, eastern oysters were analyzed and found to contain 151 p.p.m. (parts per million) DDT (52). 

Reproductive disorders in humans are known to be caused by more than 100 different individual chemicals and are suspected to be caused by some 200 more. Table 23.1 lists some of these compounds and their Kqw values. W As can be seen from this table, many different types of chemicals containing far different functional groups cause reproductive disorders. These include aliphatic and aromatic hydrocarbons, glycol ethers, chlorinated hydrocarbons, pesticides, and heavy metals. Both lipophilic and hydrophilic compounds are contained in the list. Some of the chemicals are rapidly metabolized, whereas others accumulate in adipose tissue and are stored in the body for long periods of time. The mechanisms by which many of these chemicals act remain unknown. 

---