Metal mining and birth defects: a case-control study in Lubumbashi, Democratic Republic of the Congo

Abstract

Background Widespread environmental contamination caused by mining of copper and cobalt has led to concerns about the possible association between birth defects and exposure to several toxic metals in southern Katanga, Democratic Republic of the Congo (DRC). We therefore aimed to assess the possible contribution of parental and antenatal exposure to trace metals to the occurrence of visible birth defects among neonates. Methods We did a case-control study between March 1, 2013, and Feb 28, 2015, in Lubumbashi, DRC. We included newborns with visible birth defects (cases) and healthy neonates born in the same maternity ward (controls). Mothers were interviewed about potentially relevant exposures, including their partners' jobs. Various trace metals were measured by inductively coupled plasma mass spectrometry in maternal urine, maternal blood, umbilical cord blood, placental tissue, and surface dust at home. Multivariable logistic regression analyses were done to calculate adjusted odds ratios and their 95% CIs (CI). Findings Our study included 138 neonates with visible birth defects (about 0•1% of the 133 662 births in Lubumbashi during the study period) and 108 control neonates. Potential confounders were similarly distributed between cases and controls. Vitamin consumption during pregnancy was associated with a lower risk of birth defects (adjusted odds ratio 0•2, 95% CI 0•1-0•5). Mothers having paid jobs outside the home (2•8, 1•2-6•9) and fathers having miningrelated jobs (5•5, 1•2-25•0) were associated with a higher risk of birth defects. We found no associations for trace metal concentrations in biological samples, except for a doubling of manganese (Mn; 1•7, 1•1-2•7) and zinc (Zn; 1•6, 0•9-2•8) in cord blood. In a separate model including placentas, a doubling of Mn at the fetal side of the placenta was associated with an increased risk of birth defects (3•3, 1•2-8•0), as was a doubling of cord blood Zn (5•3, 1•6-16•6). Interpretation To our knowledge, this is the first study of the effects of mining-related pollution on newborns in sub-Saharan Africa. Paternal occupational mining exposure was the factor most strongly associated with birth defects. Because neither Mn nor Zn are mined in Lubumbashi, the mechanism of the association between their increased prenatal concentrations and birth defects is unclear.

Agnathia otocephaly: A case from the Katanga Copperbelt

“…The concentrations of trace metals in cord blood are shown in Supplement (2). The concentrations of Co, As, Cd, and U were markedly higher than those found in cord blood of the 60 controls infants of our case–control study (Van Brusselen et al, 2020); in contrast, the concentrations of Mn, Cu, Pb, and Zn were much lower.…”

“…First, the father of the affected child had worked as an artisanal mineworker around the time of conception. Biomonitoring studies have documented high burdens of various toxic metals in artisanal mineworkers in the area (Nemery & Banza Lubaba Nkulu, 2018), and in our case–control study of 138 neonates with visible birth defects and 108 normal neonates, all born in Lubumbashi, we demonstrated that paternal work in mining‐related jobs was an independent, strong and significant risk factor for fathering a child with a congenital malformation (Van Brusselen et al, 2020). We speculate that occupational exposure to toxic metals causes epigenetic alterations in men, thus possibly leading to malformations in their offspring (Baccarelli & Bollati, 2009).…”

“…Nevertheless, we should also consider the possibility of a teratogenic effect of metal exposure as an alternative cause, in view of the mining‐related environmental pollution existing in the area (Banza et al, 2009; Banza Lubaba Nkulu et al, 2018) and its possible contribution to birth defects (Kayembe‐Kitenge et al, 2019; Mbuyi‐Musanzayi et al, 2018; Van Brusselen et al, 2020). Two pieces of evidence are in favor of an exogenous cause for this instance of a rare congenital malformation.…”

“…The concentrations of eight elements [arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), manganese (Mn), lead (Pb), zinc (Zn) and uranium (U)] were measured, after nitric acid destruction of 200 μl blood, using inductively coupled argon plasma mass spectrometry, with quality control/quality assurance procedures, in the laboratory of the Division of Soil and Water Management of the University of Leuven, as previously done (Van Brusselen et al, 2020).…”

“…In Lubumbashi, the capital of the former Katanga province until 2015, and now the capital of the Haut‐Katanga province in the Democratic Republic of the Congo (DRC), the population is heavily exposed to metals due to pollution by mining and metallurgic industries (Banza et al, 2009). In a case–control study conducted in Lubumbashi, we found that the risk of visible birth defects was highly increased if the neonate's father had a mining‐related job (Van Brusselen et al, 2020). In the same setting, we described three cases of holoprosencephaly in whom we had suggestive evidence for a relation with antenatal exposure to toxic metals (Kayembe‐Kitenge et al, 2019).…”