2,3,7,8-Tetrachlorodibenzo-p-dioxin toxic effects and tissue levels in animals from the contaminated area of Seveso, Italy

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

The Flash Environmental Assessment Tool: worldwide first aid for chemical accidents response, pro action, prevention and preparedness

The United Nations response mechanism to environmental emergencies requested a tool to support disaster assessment and coordination actions by United Nations Disaster Assessment and Coordination (UNDAC) teams. The tool should support on-site decision making when substantial chemical emissions affect human health directly or via the environment and should be suitable for prioritizing impact reduction management options under challenging conditions worldwide. To answer this need, the Flash Environmental Assessment Tool (FEAT) was developed and the scientific and practical underpinning and application of this tool are described in this paper. FEAT consists of a printed decision framework and lookup tables, generated by combining the scientific data on chemicals, exposure pathways and vulnerabilities with the pragmatic needs of emergency field teams. Application of the tool yields information that can help prioritize impact reduction measures. The first years of use illustrated the usefulness of the tool as well as suggesting additional uses and improvements. An additional use is application of the back-office tool (Hazard Identification Tool, HIT), the results of which aid decision-making by the authorities of affected countries and the preparation of field teams for on-site deployment. Another extra use is in disaster pro action and prevention. In this case, the application of the tool supports safe land-use planning and improved technical design of chemical facilities. UNDAC teams are trained to use the tool after large-scale sudden onset natural disasters.

Industrial chemicals and the horse

Poisoning resulting from exposure to a wide variety of industrial chemicals is not a common occurrence in horses, but it does happen on occasion. A wide range of toxicosis can occur from a wide range of industrial pollutants, such as dioxin, carbon tetrachloride, and tetrachloroethylene, to heavy metals, such as cadmium and zinc. The equine practitioner must consider industrial chemical toxicosis in differential diagnoses and work with a reputable veterinary diagnostic laboratory to confirm or rule out industrial chemical poisoning.

Dioxin and furan residues in wood mice (Apodemus sylvaticus) following a large scale polyvinyl chloride (PVC) fire

A forest ecosystem was contaminated as a result of a fire involving 600 t of PVC. A wide range of 2,3,7,8-substituted dioxin and furan congeners were elevated (by up to 4-fold) on soil adjacent to the factory compared to a site 200 m from the factory perimeter. Livers of wood mice (Apodemus sylvaticus) caught on these areas were also analysed for dioxins and furans. Toxic equivalents (TEQs) were 9-fold higher in wood mice caught on the site 10 m from the factory perimeter compared with the site 200 m from the perimeter, with individual 2,3,7,8-substituted congeners being elevated by up to 30-fold. Wood mouse liver TEQs were found to be highly correlated with cadmium kidney concentrations, cadmium also being found at elevated concentrations at the accident site. There was also a significant positive correlation between wood mouse liver TEQs and relative liver weights (wet weights expressed as a percentage of total body weight). The results of this study are discussed in the wider context of dioxin contamination in the environment.

Use of epidemiology data to assess the cancer risk of 2,3,7,8-tetrachlorodibenzo-p-dioxin

Most countries have assessed the human cancer risk of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) by extrapolating from animal data. The 1600-fold variation for acceptable intakes estimated by the Americans, Canadians, and Europeans, however, indicates a large scientific uncertainty about TCDD toxicity. Regulators are attempting to use human epidemiology data to eliminate some of the limitations inherent in using animal data to quantitatively assess cancer risk in humans, particularly now that techniques for measuring TCDD levels in adipose tissue and serum are available. This paper presents an overview of the major epidemiologic studies that associate cancer with TCDD exposure. The actual exposures experienced by the study populations are emphasized. The TCDD serum levels of the Seveso, Italy, residents and of the NIOSH Dioxin Registry participants indicate that these populations hold the best promise for future assessment of the human carcinogenic risk of dioxin. Based on the animal data, however, the calculated risk from these exposures is still moderate compared with high background cancer incidence present in most industrialized countries.

Characteristics of an extraction and purification procedure for chlorinated dibenzo-p-dioxins and dibenzofurans in soil and liver

Liver is extracted with chloroform-methanol to give essentially quantitative transfer of endogenous chlorinated dibenzo-p-dioxins (CDDs) and dibenzofurans (CDFs) into the organic phase. A new procedure involving LH-20 Sephadex is used to remove most of the lipids from the extract. Soil is extracted by a simple, rapid and economical procedure giving very high recoveries of CDDs and CDFs from sandy soil, various types of clay, and humus-rich loam. Subsequent cleanup on basic and acidic alumina complete the preparation for gas chromatography-mass spectrometric analysis. The use of propylene glycol as a "keeper" and of 2,3,7-trichlorodibenzo-p-dioxin as a carrier minimizes losses during evaporation of solvents and on glass surfaces. Interactions of 2,3,7,8-CDD with organic material in loam slightly reduce recovery but there is no indication of high affinity binding sites, the losses being apparently associated with simple distribution coefficients. Special precautions needed to avoid losses of CDFs on alumina chromatography are described, and the effect of "aging" spiked soil is discussed.

The influence of soil particle adsorption on 2,3,7,8-tetrachlorodibenzo-p-dioxin biological uptake in the rabbit

A comparative study on the biological uptake in the rabbit of 2,3,7,8-tetrachloridibenzo-p-dioxin (TCDD) in different formulations, including accident-contaminated Seveso soil, was attempted. On the whole, these results indicated that soil-borne TCDD had a bioavailability lower than that of free (solvent-borne) TCDD.