Soil quality guidelines for dioxins and furans in Canada: A review and international comparison.

Polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) (collectively PCDD/Fs) are toxic and persistent contaminants produced as unintentional by-products of anthropogenic activities. Human exposure to PCDD/Fs occurs primarily through consumption of contaminated food, though point-source soil contamination can also meaningfully contribute to exposure. Environmental soil quality guidelines (ESQGs) for PCDD/Fs have been developed worldwide. In Canada, the 2002 federal ESQG of 4 ng/kg has been adopted by most provinces and is based on limited background soil data. In the remaining provinces, ESQGs derived to be protective of human health range from 15 ng/kg to 95 ng/kg. Internationally, 70% of human health protective ESQGs adopted since 2010 range from 20 ng/kg to 120 ng/kg. Considering the consistency in human health protective ESQGs observed worldwide, the ongoing inputs of PCDD/Fs to the environment and the evolving scientific understanding of PCDD/F toxicity over the last two decades, the federal ESQG appears outdated. As ESQGs are of specific importance in the management of contaminated sites, they must remain protective of human health without being unreasonably cautious. Federal agency review and update of the ESQG for PCDD/Fs appears warranted and should consider the establishment of a risk-based guideline protective of human health. [ABSTRACT FROM AUTHOR]