title: Mercury vapour (Hg(0)): Continuing toxicological uncertainties, and establishing a Canadian reference exposure level.
abstract: There are four published reference exposure levels (RELs) for Hg(0), ranging from 0.09microg/m(3) to 1microg/m(3). All RELs were derived from the same toxicological database, predominantly of male chloralkali workers. Some key factors are apparent which make the use of that database questionable for REL derivation. Occupational studies of chloralkali workers are not an appropriate basis for a REL for Hg(0). Concomitant exposure to chlorine gas (Cl(2)) diminishes uptake and effects of Hg(0) exposure. There are gender differences in Hg(0) uptake, distribution and excretion, with females at potentially greater risk from Hg(0) exposure than males. Studies of chloralkali workers focused almost exclusively on adult males. Recent investigations of dental professionals (dentists, technicians, assistants) have failed to define a threshold in the dose-response relationship linking Hg(0) with neurobehavioural outcomes, an observation generally ignored in Hg(0) REL development. Finally, there is a growing database on genetic predisposition to health effects associated with Hg(0) exposure. Based on these considerations, we propose a different key study for REL derivation, one that involved male and female dental professionals without concomitant Cl(2) exposure. Adjusting the LOEAL to continuous exposure and applying appropriate UF values, we propose a Canadian REL for Hg(0) of 0.06microg/m(3).
authors.affiliation: Contaminated Sites Division, Health Canada, Ottawa, Ont., Canada K1A 0K9.
authors.forename: G Mark
authors.initials: GM
authors.lastname: Richardson
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Brecher
authors.forename: Hugh
authors.initials: H
authors.lastname: Scobie
authors.forename: Jane
authors.initials: J
authors.lastname: Hamblen
authors.forename: John
authors.initials: J
authors.lastname: Samuelian
authors.forename: Cindy
authors.initials: C
authors.lastname: Smith
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis* / Q000493:pharmacokinetics / Q000633:toxicity; D000818:Animals; D002170:Canada; D002713:Chlorine / Q000633:toxicity; D016208:Databases, Factual; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects*; D008297:Male; D008628:Mercury / Q000032:analysis* / Q000493:pharmacokinetics / Q000633:toxicity; D019055:No-Observed-Adverse-Effect Level; D016273:Occupational Exposure; D012016:Reference Values; D012737:Sex Factors
chemical_list: D000395:Air Pollutants, Occupational; D002713:Chlorine; D008628:Mercury