ABSTRACT
Exposures to high levels of manganese by ingestion or inhalation can damage the central nervous system. However, the capacity of environmental manganese to cause neurotoxicity is of most concern following inhalation exposure. Reference exposure levels (RELs) are values developed by California EPA's Office of Environmental Health Hazard Assessment (OEHHA) to protect the general public from periodic and continual exposures to airborne toxicants. The recently revised guidelines for the development of noncancer RELs encourage the use of benchmark dose methodology where appropriate, and explicitly address the potential susceptibilities associated with early-life exposures (OEHHA, 2008). This paper describes the application of those guidelines to the derivation of RELs to protect the general public from routine 8h and chronic exposures to airborne manganese. The data were amenable to benchmark analysis and the RELs derived reflect the mounting evidence that children represent a population that is differentially susceptible to manganese toxicity.
Subject(s)
Air Pollutants, Occupational/toxicity , Inhalation Exposure/analysis , Occupational Exposure/analysis , Oxides/toxicity , Air Pollutants, Occupational/analysis , Belgium , Benchmarking , Cross-Sectional Studies , Humans , Inhalation Exposure/adverse effects , Manganese Compounds/analysis , Neurotoxicity Syndromes/epidemiology , Neurotoxicity Syndromes/etiology , No-Observed-Adverse-Effect Level , Occupational Exposure/adverse effects , Oxides/analysis , Particle Size , Threshold Limit Values , Workplace/standardsABSTRACT
Whether or not children are at higher risk from exposure to air pollutants has become a central question in regulatory toxicology. In order to examine this issue for essential metals several questions related to toxicokinetics and toxicodynamics need to be addressed. These include (1) whether exposure patterns among infants and children are likely to result in disproportionately high exposures to substances in ambient air, and (2) whether infants display special susceptibilities in comparison to the general population. In addition, differences in how developing systems handle metals compared to adults, and interactions between specific metals and other substances with common mechanisms, need to be considered. This study examined the toxicodynamic differences between adults and infants exposed to manganese via inhalation and/or dietary routes of exposure.
