Humidity and Gravimetric Equivalency Adjustments for Nephelometer-Based Particulate Matter Measurements of Emissions from Solid Biomass Fuel Use in Cookstoves

• Main Authors: Sutyajeet Soneja, Chen Chen, James M. Tielsch, Joanne Katz, Scott L. Zeger, William Checkley, Frank C. Curriero, Patrick N. Breysse
• Format: Article
• Language: English
• Published: MDPI AG 2014-06-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: nephelometer; particulate matter; humidity adjustment; gravimetric equivalent; pDR; low resource environment; biomass burning; cookstove; indoor air quality
• Online Access: http://www.mdpi.com/1660-4601/11/6/6400

Great uncertainty exists around indoor biomass burning exposure-disease relationships due to lack of detailed exposure data in large health outcome studies. Passive nephelometers can be used to estimate high particulate matter (PM) concentrations during cooking in low resource environments. Since passive nephelometers do not have a collection filter they are not subject to sampler overload. Nephelometric concentration readings can be biased due to particle growth in high humid environments and differences in compositional and size dependent aerosol characteristics. This paper explores relative humidity (RH) and gravimetric equivalency adjustment approaches to be used for the pDR-1000 used to assess indoor PM concentrations for a cookstove intervention trial in Nepal. Three approaches to humidity adjustment performed equivalently (similar root mean squared error). For gravimetric conversion, the new linear regression equation with log-transformed variables performed better than the traditional linear equation. In addition, gravimetric conversion equations utilizing a spline or quadratic term were examined. We propose a humidity adjustment equation encompassing the entire RH range instead of adjusting for RH above an arbitrary 60% threshold. Furthermore, we propose new integrated RH and gravimetric conversion methods because they have one response variable (gravimetric PM2.5 concentration), do not contain an RH threshold, and is straightforward.