On the safe levels of micro-sized particles PM1.0 in ambient air

Introduction. Micro- and nano-sized suspended particles may be toxic to humans more than larger particles. Effects of these particles can cause diseases of the respiratory, cardiovascular, endocrine and immune system, etc. There are no safety standards for micro-sized particles PM1.0 at present in the Russian Federation. The aim of this work is scientific substantiation of the safe level of micro-sized suspended particles PM1.0 in ambient air. Materials and methods. Safe PM1.0 levels in ambient air upon long-term inhalation intake were established on the base of selecting previously conducted relevant studies and assessment of the quantitative and qualitative data (assessment of study design elements, exposure levels, adverse health responses (effects), etc.) provided in them. In key studies ‘point of departure’ for exposure was established most relevant for substantiating safe PM1.0 levels; these levels were then calculated considering use of the total (complex) modifying factor. Results. Out of sixty eight publications reported the results obtained in studies with their focus on effects of PM1.0 on the health, two key studies were selected for the procedure for justifying the value of the PM1.0 safe level in ambient air, namely, Zhang et al., 2021 and Yu et al., 2020. The safe level for PM1.0 upon chronic inhalation exposure is scientifically substantiated at 0.002 mg/m3 based on establishing the values of modifying factors and calculating the total (complex) modifying factor. Limitations. The study does not provide any toxicological results. Conclusion. The proposed safe PM1.0 level in ambient air (0.002 mg/m3) has the potential for practical application in the health risk assessment as a reference concentration, as well as for use in the system for sanitary and hygienic regulation.