Predictors and respiratory depositions of airborne endotoxin in homes using biomass fuels and LPG gas for cooking

Abstract

Recent studies have highlighted presence of endotoxin in indoor air and its role in respiratory morbidities. Burning of household fuels including unprocessed wood and dried animal dung could be a major source of endotoxin in homes. We measured endotoxin levels in different size fractions of airborne particles (PM10, PM2.5, and PM1), and estimated the deposition of particle-bound endotoxin in the respiratory tract. The study was carried out in homes burning solid biomass fuel (n = 35) and LPG (n = 35). Sample filters were analyzed for endotoxin and organic carbon (OC) content. Household characteristics including temperature, relative humidity, and carbon dioxide levels were also recorded. Multivariate regression models were used to estimate the contributing factors for airborne endotoxin. Respiratory deposition doses were calculated using a computer-based model. We found a higher endotoxin concentration in PM2.5 fractions of the particle in both LPG (median: 110, interquartile range, (IQR): 100-120 EU/m3) and biomass (median: 350, IQR: 315-430 EU/m3) burning homes. In the multivariate-adjusted model, burning of solid biomass fuel (β: 67; 95%CI: 10.5-124) emerged as the most significant predictor followed by OC (β: 4.7; 95%CI: 2.7-6.8), RH (β: 1.6; 95%CI: 0.76-2.4) and PM2.5 (β: 0.45; 95%CI: 0.11-0.78) for airborne endotoxin (p < 0.05). We also observed an interaction between PM organic carbon content and household fuel in predicting the endotoxin levels. The model calculations showed that in biomass burning homes, total endotoxin deposition was higher among infants (59%) than in adult males (47%), of which at least 10% of inhaled endotoxin is deposited in the alveolar region of the lung. These results indicate that fine particles are significant contributors to the deposition of endotoxin in the alveolar region of the lung. Considering the paramount role of endotoxin exposure, and the source and timing of exposure on respiratory health, additional studies are warranted to guide evidence-based public health interventions.

Endotoxin levels and contribution factors of endotoxins in resident, school, and office environments — A review

“…Other detailed information about the selected studies is presented in Table S3 in the SM. In residential settings, the reported average concentrations of endotoxin in indoor air varied between 0.04 and 1610 EU/m 3 (Park et al, 2000(Park et al, , 2001bvon Mutius et al, 2000;Bouillard et al, 2006;Chew et al, 2006;Dales et al, 2006;Horick et al, 2006;Rao et al, 2007;Dassonville et al, 2008;Noss et al, 2008;Riggs et al, 2008;Chen and Hildemann, 2009;Reponen et al, 2010;Semple et al, 2010;Tager et al, 2010;Delfino et al, 2011;Mazique et al, 2011;Wheeler et al, 2011;Balasubramanian et al, 2012;Frankel et al, 2012a;Semple et al, 2012;Hansel et al, 2013;McNamara et al, 2013;Pavilonis et al, 2013;Adhikari et al, 2014;Bari et al, 2014;Escobedo et al, 2014;Bose et al, 2015;Barraza et al, 2016;Padhi et al, 2016). The lowest mean endotoxin concentration was reported in Maryland, USA, during summer season (Mazique et al, 2011) and the highest in Malawian maize crop residue-burning homes during cooking time (Semple et al, 2010).…”

Airborne endotoxin concentrations in indoor and outdoor particulate matter and their predictors in an urban city

“…PM 2.5 and PM 10‐2.5 are present in indoor as well as outdoor air, and are reported to have adverse effects on respiratory morbidity in asthmatic patients . Recently, some studies have analyzed the endotoxin concentrations in airborne particles, and the endotoxin concentrations in each fraction after sampling airborne PM 2.5 and PM 10‐2.5 separately according to aerodynamic diameters have been reported . The adverse effects of exposure to endotoxins in PM 2.5 and PM 10 on lung function and symptoms were reported in asthmatic children .…”

“…16 Recently, some studies have analyzed the endotoxin concentrations in airborne particles, [17][18][19] and the endotoxin concentrations in each fraction after sampling airborne PM 2.5 and PM 10-2.5 separately according to aerodynamic diameters have been reported. [20][21][22][23] The adverse effects of exposure to endotoxins in PM 2.5 and PM 10 on lung function and symptoms were reported in asthmatic children. 24 However, the methods for sampling and analyzing airborne endotoxins have not been standardized.…”

Size–segregated particulate matter inside residences of elderly in the Metropolitan Area of São Paulo, Brazil

“…The highest RDD difference was found in PM <0.25 which represented almost 29% and 17.2% higher deposition in males for seated and light exercise positions, respectively. This finding is concerning since these smaller particles show harmful effects on the human health compared with more coarse particles (Heal et al, 2012;Kumar et al, 2014;Han et al, 2016) and can favour deposition of endotoxin in pulmonary alveoli (Padhi et al, 2016).…”