Estimation of Health Risks to Residents Chronically Exposed to an Organic Hydride and Its Dehydrogenated Substance From a Hydrogen Station

Abstract

Methylcyclohexane (MCH) is one of hydrogen carriers to be used at hydrogen stations refueling to fuel cell vehicles in near future. Although storage and transportation of MCH and its dehydrogenated product, toluene (TOL) are possible under normal temperature and pressure, these substances may be emitted unintentionally from the station into the atmosphere and may cause adverse health effects to residents around the station. In this paper, we estimated atmospheric emission rates of MCH and TOL from a hypothetical hydrogen station and assessed inhalation exposures to both substances of the neighborhood using an atmosphere dispersion model. In parallel, we surveyed existing documents, determined human NOAELs of MCH and TOL for each toxicological endpoints and then selected the nerve, the blood and the kidney as toxicological endpoints of aggregate effect due to combined exposure to both substances. In order to characterize health risk due to combined exposure to MCH and TOL, we calculated hazard indices (HIs) for above three endpoints and also hazard quotients (HQs) for other endpoints. As a result, each HI for the selected effects was less than 0.1 and it is shown that chronically human health risk to the residents caused by MCH and TOL emitted from a hydrogen station will be the level that is not concerned about.