Worldwide regulatory guidance values for surface soil exposure to noncarcinogenic polycyclic aromatic hydrocarbons

Regulatory guidance values are used worldwide to control residential exposures to surface soil contamination. A total of 1791 values used in 39 nations to control exposures to eight polycyclic aromatic hydrocarbons (PAH) not normally considered to be carcinogenic (acenaphthene, acenaphthylene, anthracene, benzo(g,h,i)perylene, fluroanthene, fluorene, phenanthrene and pyrene) are examined. The guidance values vary over 5.8 to 8.3 orders of magnitude and have distributions that strongly resemble distributions of lognormal random variables. Where the U.S. Environmental Protection Agency (USEPA) has provided values, they fall near the upper end of the distributions and appear to exert influence on values from other U.S. jurisdictions. Approximately 84% of all U.S. values fall above a median PAH value. Uncertainty bounds approximated from the USEPA risk model encompass 28% of the regulatory values and these are predominantly from U.S. jurisdictions. An unusually high degree of toxicology data uncertainty for these PAH appears to be a significant factor influencing variability. The USEPA assigns its highest toxicology uncertainty factor value of 3000 to these components.