The hidden dangers lurking in groundwater

Makueni County, in semi-arid south-eastern Kenya, is a region characterised by irregular rainfall and limited surface water, resulting in a high reliance on groundwater for domestic and agricultural use.

In the region, as in many parts of the world, groundwater is vital for communities year-round but can present potential dangers in the form of both natural and human contamination. Natural contamination, such as elevated fluorine and salt levels, may result from the dissolution of elements in the local rocks. If drunk or used in cooking and food production, this can lead to poor health outcomes for residents.

A Federation University Australia researcher is playing a key role in a project to determine whether the water in the region is safe to drink and use in agriculture. Associate Professor Kim Dowling, from the School of Engineering, Information Technology and Physical Sciences, has teamed up with the University of Johannesburg and Professor Hassina Mouri, who is currently Vice President of the International Union of Geological Sciences (IUGS), to co-supervise PhD student Patrick Gevera who took in interest in the region’s water quality after growing up near the area.

Associate Professor Dowling said the prevalence of the naturally occurring fluorine in groundwater could be a blessing or a curse – depending on the quantity. Fluorine comes in many forms including a gas which forms vary rarely at the Earth’s surface. Fluoride is an ion (charged particle) that has different properties and reacts with other elements very differently.

“The reason we put fluoride in water is that it decreases the number of cavities in children's teeth. But if you have too much, it does terrible damage to teeth and bones, and in some parts of the world the groundwater has significantly elevated levels and that has significant big health impacts on people,” Associate Professor Dowling said.

“Given that we know the chemical can have positive and very negative effects, this project in Kenya is looking at groundwater and the fluorine content and how it impacts people's lives.

“If you think about the reason fluorine is in the water in the first place, Kenya is part of a rift zone, there's lots of volcanic activity and the groundwater percolates through these metamorphic and volcanic rocks. People drill down, extract the water, which can have a range of health benefits because it is not sitting at the surface, so waterborne diseases such as malaria or cholera are less of an issue. There are many good reasons to use the groundwater.”

The researchers took samples from boreholes, shallow wells, streams, and tap water used by the local population for their research, which confirmed elevated levels of fluorine and other elements.

They found that concentrations of total dissolved solids, hardness (high concentrations of particularly calcium and magnesium carbonate) high chloride and fluoride levels that exceeded the permissible drinking water limits set by both the World Health Organization (WHO) and Kenya Bureau of Standards (KEBS), were evident in more than 50 per cent of the samples.

Associate Professor Dowling said the research also uncovered a worrying gap in what the local community knew about the dangers that lurked in their water. To determine this, she said it was pivotal to have Mr Gevera engage with the communities.

“We found that most people associated the negative effects of too much fluorine with drinking salty water – not with the actual chemical compositions. So people were avoiding salty water or not drinking as much, which has other health implications,” Associate Professor Dowling said.

“This is a very real issue for communities around the world. The adverse effects of too much fluoride, it's very easy to see. Teeth get badly mottled – it can be quite dramatic and can affect a person's ability to socialise. At very high levels, skeletal fluorosis results, causing significant and painful damage to bones.” Associate Professor Kim Dowling

The researchers have recommended measures including blending the groundwater with surface water and that defluorination be considered by authorities to minimise health risks. The researchers’ study will also be expanded to look at changing the community’s perceptions of their water.

“Patrick conducted a really interesting study looking at people's attitudes and it's one of those things that always confounds me – you can present the science, but somehow you have to get into the hearts and minds of people to affect change,” Associate Professor Dowling said.

“For example, in Bangladesh, tube wells have been developed to access groundwater for drinking and cooking but some of the tube wells go into aquifers which are rich in arsenic. Safe tube wells with low arsenic are painted green and high arsenic ones are painted red.

“So being educated to use the green wells rather than the red wells and having the social engagement to make that work is important. Unfortunately, there’s a stigma associated with having a red well in your neighbourhood and so people repaint them green.  Sometimes the green wells are just too far away and so people still use red wells. Sadly, that’s human nature.”