Estimating the Causal Impact of Proximity to Gold and Copper Mines on Respiratory Diseases in Chilean Children: An Application of Targeted Maximum Likelihood Estimation.

In a town located in a desert area of Northern Chile, gold and copper open-pit mining is carried out involving explosive processes. These processes are associated with increased dust exposure, which might affect children's respiratory health. Therefore, we aimed to quantify the causal attributable risk of living close to the mines on asthma or allergic rhinoconjunctivitis risk burden in children. Data on the prevalence of respiratory diseases and potential confounders were available from a cross-sectional survey carried out in 2009 among 288 (response: 69 % ) children living in the community. The proximity of the children's home addresses to the local gold and copper mine was calculated using geographical positioning systems. We applied targeted maximum likelihood estimation to obtain the causal attributable risk (CAR) for asthma, rhinoconjunctivitis and both outcomes combined. Children living more than the first quartile away from the mines were used as the unexposed group. Based on the estimated CAR, a hypothetical intervention in which all children lived at least one quartile away from the copper mine would decrease the risk of rhinoconjunctivitis by 4.7 percentage points (CAR: - 4.7 ; 95 % confidence interval ( 95 % CI): - 8.4 ; - 0.11 ); and 4.2 percentage points (CAR: - 4.2 ; 95 % CI: - 7.9 ; - 0.05 ) for both outcomes combined. Overall, our results suggest that a hypothetical intervention intended to increase the distance between the place of residence of the highest exposed children would reduce the prevalence of respiratory disease in the community by around four percentage points. This approach could help local policymakers in the development of efficient public health strategies.

Mercury and neuromotor function among children in a rural town in Chile.

BACKGROUND: Mercury (Hg) exposure from artisanal gold mining has adverse effects on the neuromotor function in adults. However, few studies have examined this relationship in children. OBJECTIVES: To investigate the impact of Hg exposure on children's neuromotor function. METHODS: Cross-sectional data on Hg risk factors and demographics were collected from n = 288 children (response = 68.9%). Based on complete cases (CCs) (n = 130) and multiple imputations (n = 288), associations between fingernail Hg and four different neuromotor function components were calculated using multiple logistic regression adjusted for confounders. RESULTS: Of the children, 11.1, 14.9, 63.9, and 10.4% had pathologic pure motor skills, adaptive fine motor skills, adaptive gross motor skills, and static balance, respectively. No significant association between fingernail Hg and any neuromotor component was found. However, Hg burning in the household was significantly associated with children's pathologic pure motor skills (OR 3.07 95% CI 1.03-9.18). CONCLUSION: Elemental Hg exposure in the household might have adverse long-term effects on children's pure motor skills.

Risk factors for mercury exposure of children in a rural mining town in northern Chile.

OBJECTIVE: Traditional gold mining is associated with mercury exposure. Especially vulnerable to its neurotoxic effects is the developing nervous system of a child. We aimed to investigate risk factors of mercury exposure among children in a rural mining town in Chile. METHODS: Using a validated questionnaire distributed to the parents of the children, a priori mercury risk factors, potential exposure pathways and demographics of the children were obtained. Mercury levels were measured through analyzing fingernail samples. Logistic regression modeling the effect of risk factors on mercury levels above the 75(th) percentile were made, adjusted for potential confounders. RESULTS: The 288 children had a mean age of 9.6 years (SD = 1.9). The mean mercury level in the study population was 0.13 µg/g (SD 0.11, median 0.10, range 0.001-0.86 µg/g). The strongest risk factor for children's odds of high mercury levels (>75(th) percentile, 0.165 µg/g) was to play inside a house where a family member worked with mercury (OR adjusted 3.49 95% CI 1.23-9.89). Additionally, children whose parents worked in industrial gold mining had higher odds of high mercury levels than children whose parents worked in industrial copper mining or outside mining activities. CONCLUSION: Mercury exposure through small-scale gold mining might affect children in their home environments. These results may further help to convince the local population of banning mercury burning inside the households.