Comparison of Respirable Particulate (PM4) Measturements from Direct- Reading Photometric Instruments and a Gravimentric Sampling Method

The National Environmental Management: Air Quality Act of 2004 states that people have the right to clean air and a healthy environment. Residents of low-income settlements are exposed to high concentrations of indoor air pollution due to the burning of solid fuels such as low-grade coal and wood for space heating and cooking. Long term exposure leads to degradation in the quality of life experienced by the residents of these settlements. Measuring indoor air quality is typically done by implementing the use of portable and cost effective continuous monitoring instruments, such as those based on photometric (light scattering) technology. These instruments do, however, have uncertainties associated with the overestimation of particulate mass concentration. This paper focuses on evaluating the respirable PM4 mass concentration measurement within KwaDela, a low-income settlement in Mpumalanga located on the South African Highveld. This was done by comparing PM4 mass measurements from, both the DustTrak and SidePak, photometric monitoring instruments and a filter-based reference gravimetric method, as to obtain a photometric correction factor for each of the instruments. The study found that both the DustTrak and SidePak instruments significantly overestimate the particulate mass concentration. The DustTrak Model 8530 has a photometric calibration factor of 0.14 ± (0.09, 0.15) and the SidePak 0.24 ± (0.16, 0.30). When these calibration factors are applied to the initial data, there is a significant difference experienced in exposure to high levels of respirable particulate matter. Thus, these calibration factors assist in obtaining a more accurate representation of the exposure experienced within an indoor environment prone to the combustion of solid fuels.