Are interventions to reduce the impact of arsenic contamination of groundwater on human health and crop productivity in developing countries effective? (systematic review)
Within developing countries, groundwater provides an alternative drinking source to polluted surface water. However, the presence of arsenic in some groundwater sources has resulted in chronic worldwide poisoning. The aim of this review was to determine the effectiveness of field-based technologies for the removal of arsenic from groundwater in developing countries.
A structured search strategy was conducted in a range of databases. Titles, abstracts and full texts were screened using pre-defined inclusion criteria. Included studies were quality appraised prior to data extraction. The primary outcome was the percentage of effluent water samples meeting WHO guidelines for arsenic concentrations (≤0.01 mg/L). Secondary outcomes included: (a) arsenic concentrations in effluent water samples meeting the national guideline limit (≤0.05 mg/L), (b) arsenic concentrations in human tissue, and (c) knowledge and attitudes related to the interventions.
Fifty-one reports, evaluating 50 different technologies, were included. Sixty-seven percent (n = 34) of studies were conducted in Bangladesh. Fifty of the included reports were appraised as ‘weak’, with one ‘strong’ report of a randomised-controlled trial.
In summary, the effectiveness of the oxidation and filtration interventions is poor, while the evidence for coagulation, co-precipitation and filtration, subterranean and membrane and electrolytic methods is mixed. Evidence regarding adsorption and zero valent iron interventions is more persuasive with most results suggesting good evidence of effectiveness (i.e. ≥95% of samples with arsenic concentrations ≤0.01 mg/L). In particular, activated alumina and sono/three-kolshi/gagri/pitcher filters have ≥95% of samples meeting national guidelines. Disappointingly, only one study reports excellent evidence of effectiveness: BRAC (2000) for activated alumina (i.e. ≥95% of samples with arsenic concentrations ≤0.01 mg/L).
The success of each technology was highly dependent on context, especially their acceptability to users, a sense of ownership and expectations of women’s roles in society.
Most studies were poorly conducted and reported. Consequently, although some technologies met national guidelines, the evidence-base for decision-making regarding arsenic mitigation technologies at household- and community-level is weak. To improve this situation, primary research needs to be commissioned with adequate sample sizes, testing the impact of key contextual factors, using valid tools for analysis, and meeting standards for completeness of reporting.
Arsenic mitigation, Arsenicosis, Drinking water, Groundwater, Developing countries, Systematic review
Chronic arsenic pollution is now recognised as a worldwide problem, with 21 countries experiencing arsenic groundwater contamination. It is a particularly important issue in developing countries, where groundwater is generally the preferred drinking source (as an alternative to polluted surface water). Technologies to remove or mitigate arsenic contamination of groundwater include pre-oxidation, adsorption, biological removal, and deep tubewells. Whilst technologies such as these may be effective in stable conditions (for example, at a laboratory scale), their effectiveness in real-world circumstances needs to be assessed to inform policy making.
This protocol details our proposed methods for conducting a systematic review to identify, appraise, and synthesise evidence to answer the following policy-relevant questions: a) In developing countries, are interventions to reduce the impact of arsenic contamination of groundwater on human health effective?, and b) What factors enable or constrain the effectiveness of these interventions in developing countries?