Trends of Japan’s regulations on PM 2.5
(Part-time instructor, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women’s University and editorial board member of “Society of Environmental Conservation Engineering”)
In this paper, Japan’s regulations and measures against particulate matter 2.5 (PM2.5) are described.
Epidemiological research both at home and abroad confirm that PM2.5 influences daily mortality and the respiratory and cadiovascular system in cases where the concentration exceeds 15 - 20 μg/m3. Air pollution indices are gaining attention as a new method to inform the public of daily air quality conditions. In the US, air quality standards were established in 1997, and later revised in 2006. The World Health Organization (WHO) has released guidelines for safe levels of PM2.5, and the EU established a directive on PM2.5 limits in 2008. In accordance with the actions of these nations, Japan began research and studies in 1999, and in September 2009, environmental standards were established such that the annual average PM2.5 concentration must be less than 15 μg/m3 and the daily average PM2.5 concentration must be less than 35 μg/m3.
PM2.5 is defined as airborne suspended particulate matter and tiny pieces of solid or liquid matter filtered after larger particulate matter are removed, using size classification equipment to classify particles of 2.5 μm in aerodynamic diameter by 50%. It is specified that particle mass concentrations be measured by filtration or by automatic measurement that can obtain equivalent values to mass concentration measured by the manual method. The method for manual measurement of particle mass concentrations is the daily average value obtained by the effort of filter preparation, placement and recovery, and weighing. Therefore, this method does not reflect real-time values, and has a drawback. The method for automatic measurement does not have this drawback, and in many cases, automatic measurement equipment is used at many continuous monitoring stations of air pollution.
Automatic measurement instruments for PM2.5, which are on the market now, include three different types: β-ray Absorption Method (BAM), Tapered Element Oscillating Microbalance (TEOM) and Light Scattering Method (LSM). Among them, most manufacturers employ BAM. Among LSM equipment, there are hybrid-type instruments with the functions to continuously modify simultaneous measurements based on BAM. The Ministry of the Environment implemented an “Evaluation Test for the Equivalence of Automatic Measurement Instruments” for various automatic measurement instruments, developed locally and abroad, between 2010 and 2011 and the evaluation results were disclosed. Eleven automatic measurement instruments were tested with this evaluation method, and eight out of them passed. All instruments use either BAM or a hybrid form.
In a tally compiled in 2012 on PM2.5 measurement at the continuous monitoring of air pollution stations, the rate of environment standard achievement was low at approximately 33%, and it was presumed that the environmental standards were not satisfied at many locations. The annual average PM2.5 concentration all across Japan was 15.1 μg/m3 at the ambient air pollution monitoring stations and 17.2 μg/m3 at the roadside air pollution monitoring stations. At present there are only 100 locations across Japan where PM2.5 is being monitored. The Ministry of the Environment is concentrating on the maintenance of automatic measurement equipment, training of measurement engineers, technology improvement, and proper guidance of accuracy management by each local government after the equipment placement.
Finally, to reduce PM2.5 concentration, the measurement of chemical composition is essential. In 2011, the Guideline for Component Analysis of PM2.5 was formulated. Generally, the component analysis measured soluble inorganic ions (Cl-, NO3-, SO42-, NH4+), organic carbon, elemental carbon and various metal components. The area characteristics, seasonal variations and contribution to PM2.5 concentration on them were analyzed. As the accumulation of PM2.5 data and the analysis of production mechanisms advance, new areas will be elucidated, including generation source, a mechanism of secondary formation in the atmosphere and the influence on transboundary air pollution. Effective reduction strategies are hoped for.