title: Humidity and gravimetric equivalency adjustments for nephelometer-based particulate matter measurements of emissions from solid biomass fuel use in cookstoves.
abstract: 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.
authors.affiliation: Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. ssoneja@jhsph.edu.
authors.forename: Sutyajeet
authors.initials: S
authors.lastname: Soneja
authors.affiliation: Program in Global Disease Epidemiology and Control, Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. chechen@jhsph.edu.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Global Health, School of Public Health and Health Services, George Washington University, Washington, DC 20037, USA. jtielsch@email.gwu.edu.
authors.forename: James M
authors.initials: JM
authors.lastname: Tielsch
authors.affiliation: Program in Global Disease Epidemiology and Control, Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. jkatz@jhsph.edu.
authors.forename: Joanne
authors.initials: J
authors.lastname: Katz
authors.affiliation: Department of Biostatistics, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. szeger@jhsph.edu.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Zeger
authors.affiliation: Program in Global Disease Epidemiology and Control, Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. wcheckl1@jhmi.edu.
authors.forename: William
authors.initials: W
authors.lastname: Checkley
authors.affiliation: Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. fcurrier@jhsph.edu.
authors.forename: Frank C
authors.initials: FC
authors.lastname: Curriero
authors.affiliation: Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA. pbreysse@jhsph.edu.
authors.forename: Patrick N
authors.initials: PN
authors.lastname: Breysse
mesh_terms: D016902:Air Pollution, Indoor / Q000032:analysis*; D018533:Biomass; D003296:Cooking; D005390:Fires; D006801:Humans; D006813:Humidity; D009390:Nepal; D009391:Nephelometry and Turbidimetry; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012044:Regression Analysis
chemical_list: D052638:Particulate Matter