The Millennium Development Goal (MDG) targets to cut under-5 mortality rate by two-thirds by 2015 (MDG-4). It is a piece of good news that considerable gains have been achieved and many countries are reportedly on track to meet the target.
Available research documents show that sources of child deaths are shifting over time - from infectious causes, such as pneumonia, malaria, or diarrheal diseases to accidents or violence. There is perhaps little doubt that increased uptake of vaccines, reduction in vitamin A deficiency, fewer births, and better hygiene went to drive down infectious disease mortality. Immunisation against measles alone helped prevent nearly 14 million deaths between 2000 and 2012.
Contrary to conventional reasons, an eyebrow- raising news is that the causes of child deaths in Bangladesh are led by drowning. But first let's glean through some statistics on death by drowning. According to an estimate by the UNICEF, up to 46 children drown daily and 16,500 drowning deaths occur in flood-prone Bangladesh each year. This makes it the largest killer of children aged between one and 15 years (this is also true for Cambodia, Vietnam, and Thailand). Most children are two years of age, and most die within 20 metres of their homes. This striking problem may have been known for years by advocates on the ground, but the issue of child drowning barely figures on the global child health agenda. Even recent commentary about the threat of climate change and flooding tends to emphasise the risks of infectious disease (cholera, especially) even though flooding would seem to aggravate the drowning problem. The moot concern is what causes drowning?
Mahfuzar Rahman, Nazmul Sohel, Samar Kumar Hore, Mohammad Yunus, Abbas Bhuiya and Peter Kim Streatfield carried out a research on the causes of deaths by drowning. Interestingly, the authors observed a correlation between arsenic contamination and drowning of children in Bangladesh. "Drowning is the commonest cause of injury-related deaths among children aged five years worldwide, and 95 per cent of deaths occur in low- and middle-income countries (LMICs). Millennium Development Goal 4 (MDG-4) focuses on reducing mortality among children aged five years, where a major cause is identified as drowning. We postulate that arsenic contamination might impair intrauterine programming and fetal neurodevelopment. It is known that arsenic contamination readily passes from the placenta to the fetus, but not to breast milk."
This is possibly the first study which demonstrates that arsenic exposure during pregnancy via drinking water was significantly associated with increased risk of excess mortality among children aged 1-5 years due to drowning. In their cohort, 60-80 per cent of drowning deaths occurs among women who have more than one child and/or no primary education. The mechanism of this association is not known. There is no information available in the literature in this regard. However, there is published literature on the detrimental effects of arsenic exposure through drinking water on cognitive function. The first study was a cross-sectional observation on children aged 6-9 years old conducted in Thailand. It measured chronic arsenic exposure by hair samples and reported its adverse effects on children's intelligent quotient (IQ). This was followed by a number of studies in China, Taiwan, West Bengal and Bangladesh which showed similar negative association. A more recent study in the United States reported similar findings.
All these studies mainly used the Wechsler Scales of Intelligence to measure the IQ except the Chinese one. Well water arsenic concentrations have stronger association with urinary arsenic concentrations. One study in West Bengal on children aged 5-15 years old showed negative association of urinary but not water arsenic with some subtests of IQ, for example, vocabulary, object assembly and picture completion tests. We speculate that there may be a possible indirect role of prenatal arsenic exposure on increased risk of children's death due to drowning mediating through cognitive impairment. It is reported that arsenic may play a role during neurogenesis in fetal life causing neurotoxicity, which may affect cognition and intelligence in later life.
This injury can happen through several pathways such as:1) by creating oxidative stress on developing brain by interaction with estrogen or thyroid hormones that act on brain or through altering neurotransmitters role, for example, dopamine, serotonin, etc. In animal models, it is seen that basal ganglia appears to be the most sensitive region of the brain to toxins. Arsenic exposure can modify monoamine content that can subsequently affect behaviour and other brain activities including movement control, learning and memory, cognition, and emotion. Although our finding in this study about 'prenatal exposure of arsenic as a risk factor for postnatal death due to drowning' could be an incidental observation, we hypothesise that change in behaviour of children due to altered brain development in fetal life due to arsenic exposure might have some causal linkage. Taken together, we have shown an association between arsenic exposure via drinking water and increased risk of drowning mortality in early human life. Drinking water may detrimentally impact child cognition and should be further investigated in relation to excess drowning deaths wherever applicable for achieving MDG.
The authors have drawn their sample from Matlabganj upazila possibly to take advantage of the availability of demographic surveillance data thanks to the International Centre for Diarrhoeal Disease Research, Bangladesh (iccdr,b). Arsenic exposure assessment was based on information on the individuals' drinking water history and the arsenic concentration of all water sources used during pregnancy. However, a large-scale survey throughout Bangladesh would shed further light on this important aspect of child mortality in Bangladesh. The researchers themselves believe there is an effect of arsenic exposure on disease outcomes and do not believe their study findings would differ much with exclusion of these factors. However, a larger cohort study controlling all confounding factors could elucidate further magnitude of the relationship. This could also help economise the use of huge resources devoted to the prevention of death by drowning such as training on swimming skills, building awareness among parents, social mobilisation etc.
The writer is Professor of Economics at Jahangirnagar University.
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