The relation between warmer and wetter weather and diarrhoea has been well established in other parts of the world
Scientists working through the National Institute of Environmental Health Sciences, a scientific branch of the National Institutes of Health in the United States, have linked climate change to increased occurrences of diarrhoea in young children in Tamil Nadu.
The researchers studied 25 villages outside of Tiruchirappalli, which is 322 kilometres south of Chennai in Tamil Nadu, and confined the subjects of their study to children five-years-old and younger. The study lasted over two years.
The researchers found that the prevalence of childhood diarrhoea was close to three times higher during the hottest weeks of the year, as opposed to the coolest weeks. They also found a similar increase when heavy rains followed a dry period of at least 60 days. Previous studies in southern India have found associations between rainfall, particularly heavy rainfall, and diarrhoea.
According to the World Health Organization, diarrhoea is caused by a number of bacterial, viral, or parasitic organisms, which are transmitted by contaminated food, drinking water, or from person to person as a result of poor hygiene.
The scientists note that previous studies of the associations of rainfall and temperature with diarrhoea have taken place where the main source of drinking water comes from surface sources, such as rivers and lakes, where contamination could readily come from human and animal faeces.
The water supply for the villages in Tamil Nadu, however, is primarily groundwater that is pumped to elevated storage tanks, which is then pumped to public stand pipes.
Villagers typically collect water from a public stand pipe and store it in their homes. In many cases, the researchers found evidence of pathogens in stored household drinking water.
This exceeded indications of contamination found at the stand pipes. The household tanks were possibly contaminated by people dipping their dirty hands into the household water supply.
Tamil Nadu experiences months of hot, dry weather, followed by months of monsoons. During the long, dry period, human and animal faeces accumulate in the soil.
The first rains flush them into surface water. Pathogens can also remain in the mud. Young children often put their fingers or hands in their mouths, and they may infect themselves when they come into contact with mud.
The researchers report that non-latrine defecation is common in and around the villages in this study.
There is also evidence from earlier studies that heavy rain can contaminate groundwater. In Nigeria, a study found more frequent microbial contamination of groundwater during the rainy season and around facilities with poor sanitation.
Over the next several decades, the already hot climate of Tamil Nadu is expected to get even hotter, with an average increase of one degrees Celsius in the next 15 years and as much as three degrees C before the end of the 21st century.
The predictions as to rainfall are less clear, although the researchers anticipate that extreme rainfalls will become more common. In March of this year, acute outbreaks of diarrhoea occurred in the Tamil Nadu communities of Thiruthuraipoondi and Vedaranyam, Thalaigairu, and Voimedu.
Severe diarrhoea can lead to dehydration and can be life threatening, particularly for young children or individuals who already suffer from malnourishment or impaired immunity. Worldwide, there are 1.7 billion cases of childhood diarrhoea every year. Diarrhoea kills around 525,000 children per year, and is the second leading cause of death among children under five.
Across the globe, 780 million people do not have access to improved drinking water, and 2.5 billion do not have adequate sanitation. In low-income countries, children under three years experience an average of three episodes of diarrhoea every year.
Children are deprived of nutrition each time they have diarrhoea, making it a major cause of malnutrition. And in a perverse feedback cycle, those malnourished children are more likely to have repeat episodes of diarrhoea.
Links between warmer and wetter weather and diarrhoea have been found before in other parts of the world. In the Pacific Islands scientists found that warmer weather and increased rainfall were both factors in increased incidences of diarrhoea in 2001.
Similar links were found when scientists turned their attention to Botswana, but in the case of the African country, drier, not wetter, conditions were associated with an increase of diarrhoea. The scientists speculate that during drier times in Botswana there is an increase in the number of flies, and these insects serve as a means of transmission for the diarrhoeal pathogens.
Tamil Nadu may already be experiencing the extreme weather that climate change is supposed to bring. With a drought that has lasted more than 200 days at present, trains loaded with 50 wagons carrying 2.5 million litres of water chug into Chennai every day. Only four years ago, Chennai experienced the worst floods in history.
Paul Hormick is a freelance writer and an environmental advocate in San Diego, California. This column is a personal opinion and does not necessarily reflect the opinion of Down To Earth
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