Indoor levels of polycyclic aromatic Hydrocarbons from wood burning in Rural houses in western Kenya

Abstract

Western Province of Kenya has prevalence of grass-roofed traditional houses, where cooking is done in open fire places using various biomass types, which leads to accumulation of soot under the roofs. Polycyclic Aromatic Hydrocarbons (PAHs) result from incomplete combustion of organic compounds and are emitted in gaseous phase, which may adsorb on to soot particles, or particulate phase. Exposure to mixtures of . \ PAHs increases incidences of cancer in human populations. The high indoor temperatures probably cause volatilisation of the adsorbed PAHs, leading to higher continuous human exposure to PARs. Data indicate that cancer cases are rampant in the region, yet no studies had been done to show potential causes of these cancers. The objective of this study was to extract, characterize and quantify the levels of PAHs in accumulated soot in grass-roofed houses in Western Kenya and to determine the variations in concentration of PAHs in the accumulated soot with biomass type used and house age. The houses were classified according to the predominant fuel source (perennial indigenous trees, exotic trees, shrubs and crop residues, and dung), and house age (0-5, 5-10, >10 years). The study design was factorial two, laid out in randomised complete block arrangements with fuel source as the main factor and house age as the second factor. The soot samples, collected from four houses in each sampling unit, were extracted by Soxhlet using dichloromethane, cleaned on silica gel column and analyzed by gas chromatography using open tubular capillary columns with flame ionization detector. Identification of PAHs was based on retention times of authentic standards and verified by gas chromatographic-mass spectral analysis. Quantification was based on peak area responses using the internal standard method and concentrations corrected for recovery. Separation of means and analysis of variance was done using a factorial two in randomized complete block design model. The PAHs levels significantly (P~0.05) varied with biomass type in the order: Dung ~ perennial indigenous trees ~ exotic trees ~ shrubs and crop residues. Use of dung and wood from perennial indigenous trees as fuel should be discouraged since they were higher emitters (P~0.05) of PAHs. The PAHs emitted during indoor biomass burning significantly accumulated (P~0.05) in soot with time. The accumulation patterns of some PAHs varied (P~0.05) with variation in biomass type used. These results indicate that indoor burning of biomass fuel emits. PAHs which accumulate in the accumulated soot; posing health risks to the inhabitants.