2008年-世界发展银行全球_Poisoning_the_Mind___Arsenic_Contamination_and_Cognitive_Achievement_of_Children_25页_258kb

报告摘要

Summary: Poisoning the Mind: Arsenic Contamination and Cognitive Achievement of Children

Core Content

This working paper investigates the impact of arsenic contamination on the cognitive and psychological development of children in rural Bangladesh. The study uses a nationally representative school survey dataset from 2005 to analyze how exposure to arsenic-contaminated water at home and school affects educational outcomes.

Main Findings

Negative Impact on Mathematics Scores: The study finds a negative and statistically significant correlation between mathematics scores and arsenic contamination at home, even after controlling for school-level exposure.
Gender-Specific Effects: The negative impact of arsenicosis is only significant for boys, suggesting that boys are more affected due to higher water consumption and physical activity.
No Significant Impact from School Exposure: Arsenic contamination at school has a negative but statistically insignificant effect on cognitive achievement when controlling for household exposure.
Robustness of Results: The findings remain robust when controlling for school and classroom-level unobservable factors.
Subjective Well-Being and Performance: Similar negative correlations are observed for subjective well-being (a proxy for health status) and primary-standard mathematics performance.
Social Ostracism Hypothesis: The study explores whether the negative effect is due to health status or social exclusion. It suggests that social interactions may play a role, but the effect is more likely driven by health impacts.

Key Information

Arsenic Contamination in Bangladesh

Bangladesh has the largest mass poisoning of a population due to naturally occurring inorganic arsenic in groundwater.
88–95.7% of rural households use tube wells as the main source of drinking water.
271 sub-districts in Bangladesh are affected by arsenic contamination.
31% of tube wells in affected regions have arsenic levels above WHO limits.
32 million people are exposed to arsenic-contaminated water through tube wells.

Health Effects of Arsenicosis

Arsenicosis leads to visible and invisible health issues, including skin lesions, cancer, and organ damage.
Chronic exposure to arsenic can result in reduced intellectual function, memory loss, and hallucinations.
Children are particularly vulnerable due to their higher susceptibility to arsenic effects and early exposure.

Impact on Children's Development

Four reasons for cognitive and educational impairment:
1. Poorer health status due to arsenic exposure.
2. Income shocks from reduced labor productivity.
3. Direct impact on intellectual development.
4. Social ostracism due to visible symptoms and beliefs about contagion.
Anecdotal evidence suggests that children with symptoms are less likely to attend school.

Empirical Methodology

The study uses a clustered sampling approach, selecting 60 unions across 6 divisions in Bangladesh.
Two mathematics tests were administered to grade 8 students, one at secondary-standard and one at primary-standard.
Data on arsenic contamination was collected from both school and home tube wells.
Regression models were used to estimate the effect of arsenic exposure on test scores, controlling for:
- Student and family characteristics (e.g., education, assets).
- School characteristics (e.g., teacher composition, expenditure).
- Past schooling background (e.g., primary school type, class rank).
Fixed-effects models were employed to control for unobservable factors at the union, school, and classroom levels.

Conclusion

The study highlights the adverse effects of arsenicosis on children's cognitive development, particularly boys. It emphasizes the need for policy interventions to address arsenic contamination and its long-term implications on education and health. The findings also have broader implications for other regions facing similar arsenic-related water pollution issues.