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[DHAKA] Low or moderate exposure to arsenic in drinking water is a risk factor for pneumonia in under-five children, according to a new US-supported study carried out in Bangladesh.
Findings of the study, jointly conducted by the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b) and the Mailman School of Public Health, Columbia University, and the Johns Hopkins Bloomberg School of Public Health (JHSPH) in the US, were published this month in Environmental Health.
Globally, pneumonia is the leading cause of death in under-five children. It is also the fourth largest killer disease in Bangladesh where arsenic contamination of groundwater poses a threat to some 40 million people who mainly depend on tube wells for their water supply.
Christine Marie George, lead author of the study and assistant professor, department of international health, JHSPH, tells SciDev.Net that the findings suggest that even low to moderate arsenic exposure may make children more vulnerable to pneumonia. “This is likely because the arsenic in their drinking water is weakening their immune systems, making them more vulnerable to infections.”
The study was based on arsenic concentration in urine samples of 153 children with severe and very severe pneumonia as well as 296 healthy children used as control. Samples taken on admission as well as 30 days later showed a correlation between arsenic in urine and susceptibility to pneumonia.
Mohammad Yunus, former chief of the icddr,b’s hospital in Matlab and senior consultant to the study, says the mechanism of how arsenic affects CD4 T cells and immune function is not fully understood. “However, chronic arsenic exposure reduces CD4 T cell numbers, survival and functions through oxidative stress, affecting the overall immune functions of the human body. As a result, risk of pneumonia might increase in children.”
CD4 T cells are white blood cells that are also called helper cells because they signal other types of immune cells to destroy infectious particles. If CD4 T cells become depleted, the body is left vulnerable to infections.
Qazi Quamruzzaman, leading paediatrician and chairman of the Dhaka Community Hospital Trust, tells SciDev.Net that the study needs further validation. “We are not aware of any such explanation where infants exposed to arsenic in drinking water would have increased chances of getting pneumonia. We welcome the efforts but it certainly needs more population-based studies."