Environmental exposure to metal mixtures and linear growth in healthy Ugandan children.

Emily C Moody,Ezekiel Mupere,Chitra Amarasiriwardena,Ericka G Jaramillo,Robert O Wright,Elena Colicino,Sarah E Cusick,Jose M Moran

doi:10.1371/journal.pone.0233108

Emily C Moody, Ezekiel Mupere + Show 6 more

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https://doi.org/10.1371/journal.pone.0233108

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Abstract

Stunting is an indicator of poor linear growth in children and is an important public health problem in many countries. Both nutritional deficits and toxic exposures can contribute to lower height-for-age Z-score (HAZ) and stunting (HAZ < -2). In a community-based cross-sectional sample of 97 healthy children ages 6-59 months in Kampala, Uganda, we examined whether exposure to Pb, As, Cd, Se, or Zn were associated with HAZ individually or as a mixture. Blood samples were analyzed for a mixture of metals, which represent both toxins and essential nutrients. The association between HAZ and metal exposure was tested using multivariable linear regression and Weighted Quantile Sum (WQS) regression, which uses mixtures of correlated exposures as a predictor. There were 22 stunted children in the sample, mean HAZ was -0.74 (SD = 1.84). Linear regression showed that Pb (β = -0.80, p = 0.021) and Se (β = 1.92, p = 0.005) were significantly associated with HAZ. The WQS models separated toxic elements with a presumed negative effect on HAZ (Pb, As, Cd) from essential nutrients with presumed positive effect on HAZ (Se and Zn). The toxic mixture was significantly associated with lower HAZ (β = -0.47, p = 0.03), with 62% of the effect from Pb. The nutrient WQS index did not reach statistical significance (β = -0.47, p = 0.16). Higher blood lead and lower blood selenium level were both associated with lower HAZ. The significant associations by linear regression were reinforced by the WQS models, although not all associations reached statistical significance. These findings suggest that healthy children in this neighborhood of Kampala, Uganda, who have a high burden of toxic exposures, may experience detrimental health effects associated with these exposures in an environment where exposure sources are not well characterized.

Highlights

Stunting, poor linear growth for age, is a major problem that affects children worldwide in low- and middle-income countries
In a community-based cross-sectional sample of 97 healthy children ages 6–59 months in Kampala, Uganda, we examined whether exposure to Pb, As, Cd, Se, or Zn were associated with height-for-age Z-score (HAZ) individually or as a mixture
The toxic mixture was significantly associated with lower HAZ (β = -0.47, p = 0.03), with 62% of the effect from Pb

Summary

Introduction

Poor linear growth for age, is a major problem that affects children worldwide in low- and middle-income countries. It has been associated with poor neurodevelopmental and health outcomes in childhood and into adulthood. The paradigm for understanding exposure sources of toxic metals, metalloids, and metallic elements and the research on cognitive and health effects of these exposures occurs in wealthier countries; yet due to vast differences in housing conditions, urban development and zoning laws, drainage, sanitation, and home-based industry [12], there are likely very different risk factors for exposure and more dangerous exposure patterns facing children in poorer countries. Stunting is an indicator of poor linear growth in children and is an important public health problem in many countries Both nutritional deficits and toxic exposures can contribute to lower height-for-age Z-score (HAZ) and stunting (HAZ < -2)

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