Utilizing daily excessive concentration hours to estimate cardiovascular mortality and years of life lost attributable to fine particulate matter in Tehran, Iran.

BACKGROUND

Evidence for associations between fine particulate matter (PM) and cardiovascular diseases (CVDs) in Iran is scarce. Given large within-day variations of PM concentration, using the daily mean of PM (PMmean) as exposure metric might bias the health-related assessment. This study applied a novel indicator, daily excessive concentration hours (DECH), to evaluate the effect of ambient PM on CVD mortality and years of life lost (YLL) in Tehran, the capital city of Iran.

METHODS

Hourly concentration data for PM, daily information for meteorology and records of registered cardiovascular deaths from 2012 to 2016 were obtained from Tehran, Iran. Daily excessive concentration hours of PM (PMDECH) was defined as daily total concentration-hours exceeding 35 μg/m. Using a time-series design, we applied generalized linear models to assess the attributable effects of PMDECH and PMmean on CVD mortality and YLL.

RESULTS

For an interquartile range (IQR) rise in PMDECH, total CVD mortality at lag 0-10 days and YLL at lag 0-8 days increased 2.26% (95% confidence interval (CI): 0.85-3.69%) and 23.24 (6.07-40.42) person years, respectively. Corresponding increases were 3.45% (1.44-5.49%) and 35.21 (10.85-59.58) person years for an IQR rise in PMmean. Significant associations between PM pollution (i.e., PMmean and PMDECH) and cause-specific cardiovascular health (i.e., mortality and YLL) were only identified in stroke. Subgroup analyses showed that male and people aged 0-64 years suffered more from PM pollution. Furthermore, we attributed a greater CVD burden to PMDECH (1.67% for mortality and 2.67% for YLL) than PMmean (0.63% for mortality and 0.70% for YLL) during the study period.

CONCLUSIONS

This study strengthened the evidence for the aggravated CVD mortality burden associated with short-term exposure to PM. Our findings also suggested that PMDECH might be a potential alternative indicator of exposure assessment in PM-related health investigations.