Baseline associations between exposure to metals and systolic and diastolic blood pressure among women in the Household Air Pollution Intervention Network Trial

Abstract

Lead (Pb) and cadmium (Cd) are metals that occur naturally in the environment and are present in biomass fuels, such as wood. When these fuels are burned, they can release Pb and Cd into the air, leading to exposure through inhalation. Studies of exposure to metals and health outcomes suggest harmful impacts, including cardiovascular diseases. We assessed baseline associations between Pb and Cd concentrations in dried blood spots with systolic and diastolic blood pressure (SBP, DBP) among women in the Household Air Pollution Intervention Network (HAPIN) trial. We analyzed data from three of the four HAPIN randomized controlled trial sites (Guatemala, Peru, and Rwanda), focusing on women aged 40 to 79 years living in households reliant on biomass cooking. Dried blood spots were collected, processed, and analyzed for Pb and Cd exposure; SBP and DBP were measured following international guidelines. Demographic, socioeconomic, and dietary variables were collected via standardized questionnaires administered by local field staff. Statistical analyses included multivariable linear regression to examine associations between Pb and Cd, separately, and BP, adjusting for covariates informed by a Directed Acyclic Graph. Additional analyses assessed effect modification by age and research site. There was regional variation in BP levels among women, with median SBP and DBP values higher in Rwanda (116.3 mmHg, 73.0 mmHg) and Guatemala (113.3 mmHg, 68.3 mmHg) compared to Peru (106.0 mmHg, 63.3 mmHg). Pb exposure showed positive associations with both SBP and DBP. For each log-unit increase in Pb concentration, we observed increases of 2.36 mmHg SBP (95% CI 0.51, 4.20) and 1.42 mmHg DBP (95% CI 0.16, 2.67). Cd was not associated with SBP or DBP in this analysis. Pb exposure may be an important risk factor for increased SBP and DBP, markers of cardiovascular disease risk.

Keywords: Biomass; Cadmium; Cookstove; Indoor air pollution; Lead.

Figure 1.

Boxplots of SBP (mmHg) by research site among other women with valid Pb and Cd measures at baseline (Guatemala, Peru, and Rwanda, N=272). In this boxplot Rwanda and Guatemala have the highest median values (116.3 mmHg and 113.3 mmHg) respectively compared to Peru which has 106 mmHg (values also shown in Table 2). The box represents the interquartile range with the line at the median value, the whiskers extend to data points within 1.5*IQR and the outliers are the points beyond the whiskers.

Figure 2:

Boxplots of DBP (mmHg) by research site among other women with valid Pb and Cd measures at baseline (Guatemala, Peru, and Rwanda, N=272) which presents the median values of three countries/research sites. Rwanda had the highest median of 73mmHg followed by Guatemala and Peru with 68.3mmHg, 63.3mmHg respectively (values also shown in Table 2). The box represents the interquartile range with the line at the median value, the whiskers extend to data points within 1.5*IQR and the outliers are the points beyond the whiskers.