Associations between evaporative cooling and dust‐mite allergens, endotoxins, and β‐(1 → 3)‐d‐glucans in house dust: A study of low‐income homes

Abstract

Recent work suggests that evaporative coolers increase the level and diversity of bioaerosols, but this association remains understudied in low‐income homes. We conducted a cross‐sectional study of metropolitan, low‐income homes in Utah with evaporative coolers (n = 20) and central air conditioners (n = 28). Dust samples (N = 147) were collected from four locations in each home and analyzed for dust‐mite allergens Der p1 and Der f1, endotoxins, and β‐(1 → 3)‐d‐glucans. In all sample locations combined, Der p1 or Der f1 was significantly higher in evaporative cooler versus central air conditioning homes (OR = 2.29, 95% CI = 1.05‐4.98). Endotoxin concentration was significantly higher in evaporative cooler versus central air conditioning homes in furniture (geometric mean (GM) = 8.05 vs 2.85 EU/mg, P < .01) and all samples combined (GM = 3.60 vs 1.29 EU/mg, P = .03). β‐(1 → 3)‐d‐glucan concentration and surface loads were significantly higher in evaporative cooler versus central air conditioning homes in all four sample locations and all samples combined (P < .01). Our study suggests that low‐income, evaporative cooled homes have higher levels of immunologically important bioaerosols than central air‐conditioned homes in dry climates, warranting studies on health implications and other exposed populations.

Bioaerosol and microbial exposures from residential evaporative coolers and their potential health outcomes: A review

“…However, allergen levels, with the exception of one sample, were again below the sensitization threshold. In a subsequent study of low‐income homes in Utah County, Utah, Johnston et al (2019) found Der p 1 or Der f 1 in house dust was significantly higher in EC ( n = 20) compared to AC ( n = 28) homes (OR = 2.29; 95% CI: 1.05, 4.98; p = 0.04) 93 . The authors also found a higher prevalence of dust mite allergens in EC (55%) compared to AC homes (36%).…”

“…It is important to note that the Sneller & Pinnas and Lemons et al studies did not specifically measure β‐(1 → 3)‐D‐glucan levels so that remains unknown. A recent study of low‐income homes in Utah (USA) by Johnston et al (2019) found house dust β‐(1 → 3)‐D‐glucan concentration (μg/mg) and surface load (μg/m 2 ) were 2.65‐fold and 3.64‐fold higher, respectively, in EC ( n = 20) compared to AC ( n = 28) homes 93 …”

“…Johnston et al (2017), in a study of middle‐income homes in Utah County, Utah, found house dust endotoxin levels (EU/mg) and endotoxin surface loads (EU/m 2 ) three to six times higher in EC ( n = 18) compared to AC ( n = 22) homes 92 . In a recent follow‐up study, Johnston et al (2019) 93 reported similar findings among low‐income homes in the same county. In this study, house dust endotoxin levels (EU/mg) and endotoxin surface loads (EU/m 2 ) were approximately three times higher in EC ( n = 20) compared to AC ( n = 28) homes.…”

“…homes (OR = 2.29; 95% CI: 1.05, 4.98; p = 0.04). 93 The authors also found a higher prevalence of dust mite allergens in EC (55%) compared to AC homes (36%). However, allergen levels were again below the 2.0 μg per gram threshold for sensitization for all but two samples.…”

“…49 As with bacterial endotoxin, understanding the influence of ECs on indoor β-(1 → 3)-D-glucan levels is severely limited by the low number of homes for which data are reported in the literature. While there is some evidence that ECs are associated with higher levels and more diverse species of fungi, the study by Johnston et al (2019) is the only study that we are aware of where β-(1 → 3)-D-glucan levels are reported. Furthermore, studies on associations between ECs and fungi and β-(1 → 3)-D-glucan levels are limited to states in the Western U.S., and therefore may not be gerneralizable to homes in other regions.…”