Dioxins contamination incident

Two days after the disaster, nearby residents were warned not to eat any vegetables from their gardens. Eour days after the disaster, the Technical Director of Givaudan in Geneva informed the Technical Director of ICMESA that the samples contained traces of TCDD. Authorities were told much later about the TCDD. The Seveso disaster resulted in the highest known TCDD exposure to residential populations, and has possibly been the most systematically studied dioxin contamination incident in history. 

On occasions, animal feed has been suspected of deliberate contamination. Incidents involving contamination of animal feed by industrial by-products such as polycylic aromatic hydrocarbons (PAHs) and combustion products such as dioxins are not uncommon. A problem with animal feed is that there is sometimes inadequate control over the provenance of feed constituents. For example, spent cooking oil from food-processing plants is a legitimate feed component. Unfortunately, the temptation for the unscrupulous to dispose of other unwanted oils in this way is too great for some. In many cases such adulterants are probably diluted to such an extent that they are undetectable by conventional chemical analyses. Nevertheless, they may still represent a longterm cumulative hazard to consumers of products from animals fed on such material. 

Bopp RF, Gross ML, Tong H, et al. 1991. A major incident of dioxin contamination Sediments of New Jersey Estuaries. Environ Sci Technol 25 951-956. 

Numerous incidents of dioxin contamination have resulted in a high level of public awareness and concern. This concern carries over into present efforts to implement cleanup actions and conduct disposal operations. 

The wide dispersal of the dioxin-like chemicals throughout the environment is primarily the result of atmospheric transport and deposition. Eventually the dioxin-Uke chemicals become adsorbed to dust particles and surfaces and are deposited in sediments. The two primary pathways for dioxin-like chemicals to enter the food chain are from the air-to-plant-to-animal and from water-and sediment-to-fish. A third route for dioxin-Uke chemicals to enter the food chain is through the accidental contamination incidents resulting from inappropriate handling and processing of feed and food substances. It has been estimated that more than 90% of human exposure to dioxin and dioxin-like chemicals is through the ingestion of contaminated food substances. ... 

The initial concern for the possible hazard to humans exposed to 2,4,5-T was precipitated by teratologic studies conducted by Bionetics Research Institute under contract from The National Cancer Institute (2). In these studies, large doses of 2,4,5-T were administered to pregnant rats and mice for nine of the 21 days of pregnancy. The incidence of fetal abnormalities was slightly higher in the treated animals than in control animals. Later tests indicated that these abnormalities (cleft palate) may have been caused by 27 8 ppm of 2,3,7,8-tetrachloro-dibenzo-p-dioxin present as a contaminant in the 2,4,5-T sample used in the Bionetic study (3). After the results of the study were made known, the Panel on Herbicides of the President s Science Advisory Committee studied the total 2,4,5-T situation. The report of this committee was published in March, 1971 (4). 

There have been occasions in which relatively large quantities of dioxins were released as the result of chemical or industrial accidents. Explosions at chemical plants in Seveso, Italy, in 1976 and at Bhopal, India, in 1984 are examples of such incidents. High levels of dioxin have also been found in animal feed on a few occasions the source and mechanism of this contamination have not always been clear. 

Another development is due to the interest in polychlorodibenzofurans, spurred by their occurrence as environmental contaminants. Polychloro-phenols are manufactured in large amounts (150,000 tons per annum) and find a wide range of uses. The usual method of manufacture involves the hydrolysis of chlorobenzenes, and side reactions, favored by high temperature, can lead to the production of polychlorodibenzofurans and poly-chlorodibenzo-p-dioxins. The Seveso incident is well known." Polychloro-biphenyls are also widely used industrial chemicals, particularly in heat exchange systems, and their pyrolysis leads to the formation of polychloro-dibenzofurans. Polychlorodibenzofurans have also been detected in the fly ash and flue gases of incinerators and industrial heating plants. The most toxic of the polychlorodibenzofurans are 2,3,7,8-tetra-, 1,2,3,7,8-penta-, and 2,3,4,7,8-pentachlorodibenzofuran, and an extensive literature exists on the environmental pollution and the results of human exposure to these substances. A particularly tragic example of the latter occurred in 1968 in the Fukuoka prefecture of Japan after consumption of rice oil contaminated with a commercial polychlorobiphenyl. 

Schecter A. 1983. Contamination of an office building in Binghamton, New York, by PCBs, dioxins, furans, and biphenylenes after an electrical panel and electrical transformer incident. Chemosphere 12 669-680. 

In the Times Beach incident, a waste oil dealer removed about 20,000 gal of oil contaminated by 30 ppm of 2,3,7,8-tctrachlorodibcnzo-p-dioxin from a hexachlorophene manufacturing plant, (a) What mass of dioxin was involved (b) Some of this oil was sprayed in horse arenas, and in some spots in these arenas, the soil dioxin concentration was about 2000 ppb. What mass of this soil needed to be ingested by a 100 g guinea pig to reach the LD50 of 0.6 pg/kg ... 

The potential toxicity of PCBs to humans first came into the public arena in 1968, when over 1,500 people around Fukuoka in south-west Japan were poisoned by eating food cooked in rice oil contaminated with PCBs. This was not a single (acute) poisoning incident as the victims used the contaminated rice oil for cooking for some three months. The oil had become contaminated with PCBs as a result of a leak in the machinery in the plant producing the rice oil. People started to suffer from various diseases, and the illness became known as Yusho disease (meaning rice oil disease). Most prominent was chloracne, a severe effect on the skin which is also caused by dioxins. Babies born to women who were exposed also showed symptoms of the disease. Eventually some 2,000 cases of Yusho disease were recorded. 

PCDFs are very similar to dioxins and, like them, are very toxic, especially 2,4,7,8-tetrachlorodibenzofuran, although this is not quite as toxic as TCDD. They have been found to be contaminants of PCBs and in the Yusho and Yu-Cheng poisoning incidents were more abundant in the PCBs than was usual. As with dioxins and PCBs, there are many different isomers and congeners. 

In this example knowledge of the level of exposure of the victims, and measurement of the levels in their bodies, were particularly important. This is often lacking in such situations, which makes it virtually impossible to relate effects to a particular chemical. It should also be noted that the exposure levels in these two incidents were relatively high. Levels of PCBs (and dioxins) that are present in the environment and might contaminate food, for example, are monitored and are... 

Bernard, A., Broeckaert, F., De Poorter, G. et al. (2002). The Belgian PCB/dioxin incident analysis of the food chain contamination and health risk evaluation. Environ. Res. 88 1-18. 

Polychlorinated dibenzo-p-dioxins, or PCDDs, are highly toxic substances that are present in trace amounts as byproducts of some chemical manufacturing processes. They have been implicated in a number of environmental incidents—for example, the chemical contamination at Love Canal and the herbicide spraying in Vietnam. The structure of dibenzo-p-dioxin, along with the customary numbering convention, is... 

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