Abstract:
BACKGROUND : The health effect of air pollution is rarely quantified in Africa, and this
is evident in global systematic reviews and multi-city studies which only includes South Africa.
METHODS : A time-series analysis was conducted on daily mortality (cardiovascular (CVD) and
respiratory diseases (RD)) and air pollution from 2006–2015 for the city of Cape Town. We fitted
single- and multi-pollutant models to test the independent effects of particulate matter (PM10),
nitrogen dioxide (NO2), sulphur dioxide (SO2) and ozone (O3) from co-pollutants. RESULTS : daily
average concentrations per interquartile range (IQR) increase of 16.4 g/m3 PM10, 10.7 g/m3 NO2,
6 g/m3 SO2 and 15.6 g/m3 O3 lag 0–1 were positively associated with CVD, with an increased
risk of 2.4% (95% CI: 0.9–3.9%), 2.2 (95% CI: 0.4–4.1%), 1.4% (95% CI: 0–2.8%) and 2.5% (95% CI:
0.2–4.8%), respectively. For RD, only NO2 showed a significant positive association with a 4.5% (95%
CI: 1.4–7.6%) increase per IQR. In multi-pollutant models, associations of NO2 with RD remained
unchanged when adjusted for PM10 and SO2 but was weakened for O3. In CVD, O3 estimates were
insensitive to other pollutants showing an increased risk. Interestingly, CVD and RD lag structures
of PM10, showed significant acute effect with evidence of mortality displacement. CONCLUSION : The
findings suggest that air pollution is associated with mortality, and exposure to PM10 advances the
death of frail population.
Description:
DATA AVAILABILITY STATEMENT : Exposure data are available for download on the South African Air
Quality Information System (SAAQIS) website; however, restrictions apply to the health outcome data.
SUPPLEMENTARY MATERIAL : This document tabulates the correlations
among environmental variables and provides estimates for the two-day means of the four pollutants
by age group, sex and season, and for the lag structures of effects over 21 days by age group.