Establishing indicators for assessing non-carcinogenic risks under chronic inhalation exposure to benzene and average annual mpc for benzene as per health risk criteria

Recently multiple new toxicological and epidemiologic data on negative effects produced by chemicals have become available; given that, it is necessary to improve quantitative criteria applied in health risk assessment. It is advisable to revise previously established reference concentrations and to make more precise lists of organs and systems affected by a chemical in concentrations which are either equal to reference one or exceed it. Our research aim was to establish a reference concentration for benzene and additional quantitative indicators of its effects (additional reference concentrations) on specific organs and systems under chronic inhalation exposure; another aim was to determine average annual MPC verified as per permissible lifetime carcinogenic risk using evolution models. The research allowed recommending 0.005 mg/m3 to be used as a reference concentration under chronic inhalation exposure to benzene; a decrease in quantity of B-lymphocytes was recommended as a critical effect since this decrease might produce negative effects on the blood and immune system. Additional reference concentrations for benzene were fixed at 0.007 mg/m3 for the liver as a critical organ and 0.012 mg/mg3 for violated process of organism development as a critical effect. They can be used as additional indicators for assessing non-carcinogenic health risks under chronic inhalation exposure to benzene in its elevated concentrations. Our research results were used to substantiate average annual MPC for benzene in ambient air; its recommended value was 0.005 mg/m3 since it provided safety (absence of impermissible (unacceptable) lifetime health risk), probable carcinogenic effects taken into account