Long-term exposure to black carbon and mortality: A 28-year follow-up of the GAZEL cohort

BACKGROUND

The current evidence on health effects of long-term exposure to outdoor airborne black carbon (BC) exposure remains scarce.

OBJECTIVES

To examine the association between long-term exposure to BC and mortality in a large population-based French cohort, with 28 years of follow-up.

METHODS

Data from the GAZEL cohort were collected between 1989 and 2017. Land use regression model with temporal extrapolation wa used to estimate yearly BC and PM_2.5 exposure at the residential addresses from 1989 until censoring for 19,906 participants. Time-varying Cox models with attained age as time-scale was used to estimate the associations between BC and all-cause and cardiovascular mortality, after adjusting for individual and area-level covariates. To handle confounding by PM_2.5, we used the residual of BC regressed on PM_2.5 as an alternate exposure variable. For all-cause mortality, we also examined effect modification by sex, smoking status, BMI and fruit/vegetable intake.

RESULTS

The median of 20-year moving average of BC exposure was 2.02 10^-5/m in study population. We found significant associations between BC exposure and all-cause mortality (n = 2357) using both 20-year moving average of BC and residual of BC, with corresponding hazard ratios (HR) of 1.14 (95 %CI: 1.07-1.22) and 1.17 (95 %CI: 1.10-1.24) for an inter-quartile range (IQR) increase (0.86 10^-5/m for BC and 0.57 10^-5/m for residual of BC). We found a similar association between BC and cardiovascular mortality (n = 277) with a HR of 1.15 (95 %CI: 0.95-1.38). The dose-response relationship between BC and all-cause mortality was monotonic but nonlinear with a steeper slope at high BC levels. In addition, the effect of BC was higher among never-smokers and among those having fruit/vegetables less than twice a week.

CONCLUSIONS

There was a positive association between long-term exposure to BC and increased mortality risk, reinforcing the emerging evidence that BC is a harmful component of PM_2.5.

Risks of developing cancer relative to living near a municipal solid waste landfill site in Montreal, Quebec, Canada

In this study, we sought to determine whether men who lived near the Miron Quarry municipal solid waste landfill site in Montreal, Quebec, Canada, were at higher risk for developing cancer than individuals who lived at more remote locations. Subjects were selected from a previously completed population-based, interview, cancer case-control study of men who lived in metropolitan Montreal. Thirteen sites of cancer (n = 2 928 subjects) and a population-based control group (n = 417) were analyzed. We used the exact street address at the time of diagnosis to classify subjects by geographic zones and distance from the site. We used unconditional logistic regression to estimate odds ratios (ORs) and associated 95% confidence intervals (CIs) for each site of cancer, adjusted for key covariates. In the exposure zone nearest to the site, elevated risks were found for cancers of the pancreas (adjusted OR = 1.4 [95% CI = 0.8, 2.6]); liver (OR = 1.8 [95% CI = 0.8, 4.3]); and prostate (OR = 1.5 [95% CI = 1.0, 2.1]). A high risk was also found for pancreatic cancer (OR = 1.7 [95% CI = 0.9, 3.5]) and the non-Hodgkin's lymphomas (OR = 1.5 [95% CI = 0.8, 2.6]) in a subexposure zone approximately downwind from the site. We used distance from the site as another exposure metric, and higher-than-expected risks were found for pancreatic cancer (OR for living within 1.25 km of the site [OR<1.25km] = 2.2 [95% CI = 1.0, 4.6]); liver cancer (OR<1.5km = 2.1 [95% CI = 0.8, 5.3]); kidney cancer (OR<2 km = 1.4 [95% CI = 0.9, 2.3]); and the non-Hodgkin's lymphomas (OR<1km = 2.0 [95% CI = 1.0, 4.0]). Data from this study and from a previous investigation at the same site suggest that men who lived near this landfill site may have been-and may continue to be-at excess risk of cancers of the liver, kidney, pancreas, and non-Hodgkin's lymphomas.