Probabilistic Estimation of Regional Dietary Exposure to Dioxins in Fish in Japan on the Basis of Market and Fish Distribution Network Data

ABSTRACT

Dietary consumption of fish is the greatest contributor to dioxin exposure of the general population in Japan. Unlike with other routes of exposure to dioxins, exposure via foodstuffs does not necessarily occur from local sources. Clarifying the distribution of fish from the catch area to local markets helps to control dioxin exposure from the head of the distribution chain down. We analyzed the data from 30 major central wholesale fish markets to determine both the market share of fish by catch area and the market share of major fish types in fish consumption markets. Probabilistic estimation of dietary exposure of the general population to dioxins in fish was conducted in seven regions in Japan. Probabilistic density functions (PDFs) were assigned to express the variability of data from monitoring of dioxin levels in fish by catch area or by fish type. From histograms of dioxin levels in fish by catch area, the mean and 5th to 95th percentile range of dietary exposure to dioxins in the region with the largest 95th percentile value were estimated, respectively, as 55.5 and 12.9–172.9 pg-TEQ/day. No statistically significant differences in dietary exposure to dioxins in fish were observed among the seven regions. Some specific coastal catch areas and some types of fish that had a greater impact than others on exposure were pinpointed for each region.

Key Words:

• probabilistic estimation
• geographic variability
• dietary exposure
• dioxins
• fish
• distribution network

ACKNOWLEDGMENTS

This research was supported by funds for the Investigation of Human Exposure to Dioxins, provided by the Ministry of Environment of Japan. This study received a quantity of valuable statistical data from the Ministry of Agriculture, Forestry, and Fishery of Japan and 30 central wholesale markets. The authors are grateful for their help.

Notes

¹“Central wholesale market” refers to a wholesale market established with the approval of the Minister of Agriculture, Forestry, and Fisheries in prefectures or cities with populations exceeding 200,000. “Local wholesale market” refers to a wholesale market established with the approval of the prefectural governor and includes markets (other than the central wholesale market) above a certain size.