Few studies have examined indoor air quality in First Nations communities and its impact on cardiorespiratory health. To address this need, we conducted a crossover study on a First Nations reserve in Manitoba, Canada, including 37 residents in 20 homes. Each home received an electrostatic air filter and a placebo filter for 1 week in random order, and lung function, blood pressure, and endothelial function measures were collected at the beginning and end of each week. Indoor air pollutants were monitored throughout the study period. Indoor PM 2.5 decreased substantially during air filter weeks relative to placebo (mean difference: 37 lg/m 3 , 95% CI: 10, 64) but remained approximately five times greater than outdoor concentrations owing to a high prevalence of indoor smoking. On average, air filter use was associated with a 217-ml (95% CI: 23, 410) increase in forced expiratory volume in 1 s, a 7.9-mm Hg (95% CI: À17, 0.82) decrease in systolic blood pressure, and a 4.5-mm Hg (95% CI: À11, 2.4) decrease in diastolic blood pressure. Consistent inverse associations were also observed between indoor PM 2.5 and lung function. In general, our findings suggest that reducing indoor PM 2.5 may contribute to improved lung function in First Nations communities. Practical ImplicationsIndoor air quality is known to contribute to adverse cardiorespiratory health, but few studies have examined indoor air quality in First Nations communities. Our findings suggest that indoor PM 2.5 may contribute to reduced lung function and that portable air filters may help to alleviate these effects by effectively reducing indoor levels of particulate matter.

The zooplankton and zoobenthos were investigated in six lakes in the Sudbury area of Ontario in which pH values lay between 4.05 and 7.15. Zooplankton showed a significant reduction in species and numbers at the lower pH levels; the Rotifera showed the greatest changes. Zooplankton diversity index (DI) declined sharply below pH 5.3. Percentage similarity of community (PSc) and coefficient of community (CC) values were highest between lakes closest in pH, reflecting progressive changes in species composition.Significant relationships were found between the zooplankton standing crop and chlorophyll a concentrations and the zooplankton standing crop and areal primary productivity. Dry weights for Holopedium gibberum and Diaptomus minutus were lowest in the most acidic lakes. No significant relationship between body length or egg ratio, and lake pH were found for D. minutus.The zoobenthos was represented by a variety of taxa; however, only genera belonging to the Oligochaeta and Tendipedidae were represented in all study lakes. Zoobenthos DI showed only a slight decrease below a pH of 4.9. PSc and CC values for the zoobenthos displayed similar though not as distinct patterns as those found in the plankton.

The effects of acidity on primary production, species composition, and abundance of phytoplankton were investigated in six lakes in the Sudbury area of Ontario, where pH values lay between 4.05 and 7.15. Significant relationships showing an increase in water transparency and decrease in chlorophyll a concentration with declining pH were found. Percentage similarity of community (PSc) and community coefficient (CC) values were highest between lakes closest in pH, reflecting progressive changes in species composition. As the pH declined, Chlorophyta diminished in importance and the Cyanophyta became dominant. The phytoplankton diversity index (DI) remained relatively unchanged between pH values of 7.0 to 5.0 but decreased at lower values. Primary production in milligrams C metre−3 hour−1 was reduced in lakes below pH 5.5; however, as a result of the increase in depth of euphotic zone accompanying more acidic conditions, primary production in milligrams C metre−2 hour−1 remained high down to pH 4.4, below which it was drastically reduced.

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