The effect of weatherization on the microbiology of the residential built environment in Upstate New York

Background: Weatherization of residential homes is a popular retrofit procedure to improve the energy efficiency of older homes by reducing building leakage. Several studies have evaluated the effect of weatherization on indoor pollutants such as formaldehyde and radon. Few studies have evaluated the effect of weatherization on indoor particulates and microbial exposures. Objective: We compared the effect of change in building leakage on indoor pollutants and bacterial community in weatherized compared to non-weatherized residential homes. Methods: Nine weatherized and eleven non-weatherized single-family homes in Tompkins County, New York were sampled twice: before and after the weatherization procedures for case homes, and at least 3 months apart for control homes that were not weatherized. We measured radon levels, environmental conditions, and collected air, carpet dust, and floor surface samples to assess the indoor microbiome. Results: We found a significant increase in living area and basement radon levels of weatherized homes compared to control homes (p = 0.03, 0.019). The indoor microbiome also became less similar to the outdoor community after weatherization. Compared to the changes in ventilation rate, temperature, relative humidity, and occupancy, season was a more predictive measure of indoor bacterial concentration. Conclusion: Ventilation rate reduction from weatherization procedures led to an increase in indoor radon levels. However, it did not affect indoor particulate mass concentration, indoor airborne bacterial load, and have very minimal effect on the microbiome of residential homes. Changes in bacterial concentration are more sensitive to seasonal variations, whereas radon levels are more sensitive to ventilation rate.

背景：住宅气密性改造（weatherization）是一项常用的旧房节能改造工序，通过降低建筑渗漏量来提升老旧住宅的能源利用效率。已有多项研究评估了气密性改造对甲醛、氡等室内污染物的影响，但针对该改造对室内颗粒物与微生物暴露影响的研究尚少。
研究目的：本研究对比实施气密性改造的住宅与未实施改造的住宅，分析建筑渗漏变化对室内污染物及细菌群落的影响。
研究方法：本研究在纽约州汤普金斯县选取9栋实施过气密性改造的独栋住宅与11栋未实施改造的独栋住宅，共开展两次采样：实验组住宅分别在气密性改造工序前后完成采样，对照组住宅则至少间隔3个月完成两次采样。本研究测定了氡浓度与环境参数，并采集空气、地毯粉尘及地面表面样本以分析室内微生物组。
研究结果：相较于对照组住宅，实施气密性改造的住宅的居住区域与地下室氡浓度显著升高（p=0.03、0.019）。气密性改造后，室内微生物组与室外微生物群落的相似性亦有所下降。与通风速率、温度、相对湿度及居住人数的变化相比，季节因素对室内细菌浓度的预测性更强。
结论：气密性改造工序会导致通风速率降低，进而使室内氡浓度升高。但该改造并未对室内颗粒物质量浓度、室内空气细菌载量产生影响，且对住宅室内微生物组的影响极微。室内细菌浓度的变化对季节波动更为敏感，而氡浓度则对通风速率的变化更为敏感。