Relationship between ambient black carbon and daily mortality in Tehran, Iran: a distributed lag nonlinear time series analysis.

Purpose: The aim of the present study was to investigate the effect of short-term exposure to ambient black carbon (BC) on daily cause-specific mortality, including mortality due to respiratory, cardiovascular, ischemic heart and cerebrovascular diseases in Tehran, Iran.
Materials and Methods: Daily non-accidental death counts, meteorological data and hourly concentrations of air pollutants from 2014 to 2017 were collected in Tehran. A distributed lag non-linear model was used to assess the association between exposure to BC and daily mortality.
Results: The mean daily BC concentration during the study period was 3.96 ± 1.19 µg/m ³ . The results indicated that BC was significantly associated with cardiovascular, ischemic heart disease, and cerebrovascular mortality, but not with respiratory mortality. In first model, each 10 µg/m ³ increase in at lag 3, lag 4 and lag 5 were associated with cardiovascular mortality in 16-65 year age group with the relative risks (RRs) of 1.17 (95 % CI: 1.02-1.33), 1.17 (95 % CI: 1.04-1.31) and 1.12 (95 % CI: 1.02-1.24), respectively. The highest mortality rate per 10 µg/m ³ increase in exposure was found for ischemic heart diseases with RR of 3.98 (95 % CI: 1.04-1.81, lag 01) for 16-65 age group. Cerebrovascular mortality was associated with 10 µg/m ³ increases in non-cumulative exposure with RR of 1.17 (95 % 1.009-1.35, lag 5) in the age group ≥ 65 years. In the second model for a 10 µg/m ³ increase in BC, cardiovascular mortality at specific lag days (5 and 6 days) in the age group ≤ 16 years were associated with RR of 1.34 (95 % CI 1.08-1.66) and 1.35(95 % CI 1.02-1.77), respectively.
Conclusions: This study in Tehran found significant effects of BC exposure on daily mortality for cardiovascular, ischemic heart disease, cerebrovascular disease.
Supplementary Information: The online version contains supplementary material available at 10.1007/s40201-021-00659-0.
Competing Interests: Conflict of interestThe authors of this article declare that they have no conflict of interests.
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