Polychlorinated biphenyls (PCBs) are a widespread class of persistent organic chemicals that accumulate in the environment and humans and are associated with a broad spectrum of health effects. PCBs were widely used for many applications, especially as dielectric fluids in transformers, capacitors and coolants. Due to their toxicity and classification as persistent organic pollutants, processing and distribution of PCB has been prohibited in almost all industrial countries since the late 1980s but they still can be released into the environment from building paint and sealants and poorly maintained hazardous waste sites that contain PCBs. People are exposed to PCBs primarily through contaminated food.
Depending on the number of chlorine atoms and their position, 209 PCB congeners are possible. Based on structural characteristics and toxicological effects, PCBs are divided into dioxin like PCBs (DL PCBs) showing toxicological properties similar to dioxins and non dioxin-like PCBs (NDL PCBs) which do not share the dioxin’s toxic mechanism. Some NDL PCBs have been shown to elicit neurological, endocrine, immunological and carcinogenic effects. Several international agencies classify PCBs as probably carcinogenic to humans.
In evaluating the contamination situation, six congeners (# 28, 52, 101, 138, 153, and 180) were chosen as indicators for the occurrence of NDL PCBs. The Scientific Panel on Contaminants in the Food Chain of EFSA (CONTAM Panel) noted in its Scientific Opinion related to the presence of NDL PCBs in feed and food that the sum of the six indicator PCBs represented about 50 % of the total NDL-PCB in food. The EU Commission is currently discussing to lay down maximum levels for the sum of the six indicator NDL-PCBs in food and feed.
In 2002 the European Commission prescribed a list of actions to be taken to reduce the presence of dioxins and DL PCBs in food and feed and later introduced regular monitoring by Member States of food and feed, including, if possible, also NDL PCBs. Data on the presence of dioxins and PCBs in food and feed have been reported on a regular basis to the Commission. In April 2008 the Commission handed the collected information to the European Food Safety Authority (EFSA) for assessment.
A total of 11,214 food and 1,349 feed samples collected in the period 1995 2008 from 18 EU Member States, Iceland and Norway were retained for a detailed analysis. Overall, 18.8 % of the results for single congeners were below the limit of quantification (LOQ). PCB-153 and PCB-138 contributed the most to the sum of the six NDL-PCB congeners followed by PCB 180, PCB 28, PCB 101 and PCB 52 in that order, but relatively high variations were observed for each congener throughout food and feed groups. The contribution of PCB-153 and PCB-138 together consistently comprised at least 50% of the overall sum of the six congeners in each food group.
The highest mean of food contamination levels were observed in several fish and fish product categories followed by products of terrestrial animals. The lowest values were found in fruits and vegetables. Similarly the highest mean of feed contaminations were found in fish oil while most of other feed groups had mean levels below 1 µg/kg.
Regression analysis showed that the sum of the six NDL-PCBs were on average close to five times higher than the sum of the 12 DL-PCBs. This relationship varied across food groups and is presumably related to the origin of samples and the contamination source.
The current assessment includes results from both random and targeted monitoring but a clear separation of the two sampling groups was not possible. The lack of such sampling information and the irregular coverage of food and feed groups over time did not allow for an accurate time trend analysis to be performed. To improve the validity of any assessment of the presence of dioxins and PCBs in food and feed in Europe it is important to carry out random testing and separate reporting of a sufficient number of samples in each food and feed group. Targeted sampling during contamination incidences should be clearly indicated as such in the reporting.