In March of 1999, the Agency for Toxic Substances and Disease Registry (ATSDR) published their Toxicological Profile for Mercury. ATSDR established a Minimal Risk Level (MRL), which is an estimate of the amount of a chemical a person can eat, drink, or breathe each day without a detectable risk to health. MRLs are developed for health effects other than cancer. ATSDR has defined a Minimal Risk Level (MRL) for chronic exposures (more than 365 days) to mercury of 0.2 ug/m3. MRLs can be made for 3 different time periods [the length of time people are exposed to the chemical: acute (about 1 to 14 days), intermediate (from 15-364 days), and chronic (exposure for more than 364 days)]. ATSDR works closely with the Environmental Protection Agency (EPA) at both a national and regional level at sites where exposures are estimated to exceed health-based values such as MRLs.
Please read the text in the document below that is specific to “metallic mercury”, paying close attention to the highlighted text.