Impact of improved indoor air quality in Nunavik homes on children's respiratory health.

Between 2007 and 2012, hospitalization rate related to respiratory system diseases in children ≤1-year-old was near 7 times higher in Nunavik compared with the whole province of Quebec. To assess the impact of poor indoor air quality (IAQ) in residential environments on children's respiratory health, the Nunavik's intervention study investigated the impact of the optimization of ventilation systems on the incidence rates of respiratory infections in children in Nunavik. Children under 10 years were recruited and categorized according to the type of ventilation system in their home: energy recovery ventilator (ERV), heat recovery ventilator (HRV), no HRV or ERV, and control groups. Children's' medical records were analyzed over a period of 50 weeks pre- and post-intervention. Clinical diagnoses were classified into 4 categories: upper respiratory infections, lower respiratory infections, otitis media, and asthma. A decrease in respiratory infections episodes was observed in all groups following intervention with the highest impact observed for HRV systems (-53.0%). Decreases in the ERV group were not significant (-21,7%) possibly due to the presence of some volatile organic compound (such as propylene glycol) and inerrant experimental bias. Nevertheless, no significant association was found between health episodes incidence and household's behaviors or IAQ.

Indoor air quality assessment in dwellings with different ventilation strategies in Nunavik and impacts on bacterial and fungal microbiota.

Indoor air quality is a major issue for public health, particularly in northern communities. In this extreme environment, adequate ventilation is crucial to provide a healthier indoor environment, especially in airtight dwellings. The main objective of the study is to assess the impact of ventilation systems and their optimization on microbial communities in bioaerosols and dust in 54 dwellings in Nunavik. Dwellings with three ventilation strategies (without mechanical ventilators, with heat recovery ventilators, and with energy recovery ventilators) were investigated before and after optimization of the ventilation systems. Indoor environmental conditions (temperature, relative humidity) and microbiological parameters (total bacteria, Aspergillus/Penicillium, endotoxin, and microbial biodiversity) were measured. Dust samples were collected in closed face cassettes with a polycarbonate filter using a micro-vacuum while a volume of 20 m3 of bioaerosols were collected on filters using a SASS3100 (airflow of 300 L/min). In bioaerosols, the median number of copies was 4.01 × 103 copies/m3 of air for total bacteria and 1.45 × 101 copies/m3 for Aspergillus/Penicillium. Median concentrations were 5.13 × 104 copies/mg of dust, 5.07 × 101 copies/mg, 9.98 EU/mg for total bacteria, Aspergillus/Penicillium and endotoxin concentrations, respectively. The main microorganisms were associated with human occupancy such as skin-related bacteria or yeasts, regardless of the type of ventilation.

Widespread formation of toxic nitrated bisphenols indoors by heterogeneous reactions with HONO.

With numerous structurally diverse indoor contaminants, indoor transformation chemistry has been largely unexplored. Here, by integrating protein affinity purification and nontargeted mass spectrometry analysis (PUCA), we identified a substantial class of previously unrecognized indoor transformation products formed through gas-surface reactions with nitrous acid (HONO). Through the PUCA, we identified a noncommercial compound, nitrated bisphenol A (BPA), from house dust extracts strongly binding to estrogen-related receptor γ. The compound was detected in 28 of 31 house dust samples with comparable concentrations (ND to 0.30 µg/g) to BPA. Via exposing gaseous HONO to surface-bound BPA, we demonstrated it likely forms via a heterogeneous indoor chemical transformation that is highly selective toward bisphenols with electron-rich aromatic rings. We used 15N-nitrite for in situ labeling and found 110 nitration products formed from indoor contaminants with distinct aromatic moieties. This study demonstrates a previously unidentified class of chemical reactions involving indoor HONO, which should be incorporated into the risk evaluation of indoor contaminants, particularly bisphenols.