Arsenic contamination in food and water is a growing public health concern. World Health Organization has recognised the serious effects of this heavy metal on human health.
According to WHO, sustained exposure to arsenic through drinking water and food can lead to severe health issues like cancer, skin lesions, cardiovascular disease and diabetes. Exposure to it during pregnancy and early childhood affects the infant’s cognitive development.
A collaborative study by researchers from India, the UK, Germany, France and China delved into how low-level exposure to arsenic affects brain structure and functioning. The study published in JAMA Network underscores the importance of assessing arsenic levels in drinking water, as even small amounts of arsenic can harm the brain.
The study aimed to understand how environmental exposure could heighten the genetic risk for mental health disorders. “While there is a [a natural bodily] mechanism for sculpting the brain, which is a genetic programme and is heritable, we also think that the environment modifies this,” Vivek Benegal, professor of psychiatry at the National Institute of Mental Health and Neurosciences, Bengaluru, tells Happiest Health.
Various faces of arsenic
Arsenic is found naturally in groundwater and soil, says Asim Bhalerao, the CEO of Fluid Robotics, Pune, a company that analyses wastewater. In addition, coal-fired power plants release significant amounts of arsenic into the environment.
Arsenic is abundantly found in the Himalayan region, home to four major river systems: the Ganga, the Brahmaputra, the Irrawaddy, and the Mekong. Their catchment areas are the world’s significant rice-growing regions.
According to Bhalerao, urbanisation and water scarcity could have led to the gradual increase of arsenic levels in groundwater over the years. He says that arsenic is present at around 100 feet underground, where it contaminates the aquifers – the groundwater sources.
“When you are tapping into groundwater caches by digging borewells, it causes the metal to come up and [enter] drinking water sources,” he says.
A chemical conundrum
In the current study, the researchers analysed data from 1,014 individuals aged 6-23 years from the Indian Consortium on Vulnerability to Externalizing Disorders and Addictions (cVEDA) cohort. They looked at their diet patterns, socioeconomic status, BMI, urine arsenic levels and MRIs of their brains.
The team found that the participants’ average arsenic level in urine was around 9.40 microgram/litre. Exposure to arsenic and the arsenic level was found higher in participants from South India than in the Northeastern states. However, further analysis revealed that their elevated levels were linked to their dietary habits of consuming rice, egg, fish and chicken.
Children from the lower income groups were found more vulnerable to environmental exposure to arsenic. “Often these people work in environments which further expose them to more arsenic,” says Prof Benegal. Lower incomes also reflect poor access to good nutrition and increased stress in the body, which affects their body mass index, he says.
Grey matter danger
From the brain MRI scans of the participants, the researchers found that higher arsenic exposure altered grey matter volume in the brain areas associated with executive functions and learning, such as the inferior frontal cortex. The thickness of certain parts of the brain’s outer layer, the cerebral cortex, was also different.
“We found that the greater the arsenic in people’s urine, the greater were the alterations and difference in brain volume and greater the cognitive deficits found in these kids,” said Nilakshi Vaidya, the first author of the study who is a research associate at the Charité – Universitätsmedizin Berlin, Germany.
The researchers noted that arsenic exposure also disrupted the activity and interactions of the neurons (called functional connectivity) in the regions governing executive functions. Previous studies have shown that such disrupted activity occurs in attention deficit hyperactivity disorder.
The current study’s researchers also observed reduced grey matter volume in the insula and anterior cingulate cortex, which shows up as typical arsenic-related symptoms such as impaired attention, inability to take risks and speech issues.
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“There seems to be a clear association between exposure to arsenic, delay in brain development and poor cognitive functioning,” says Dr Vaidya.
Bhalerao emphasises that since arsenic exposure carries such immense health risks, “There needs to be testing for arsenic and other heavy metals in drinking water in all locations, in water treatment plants and sewage treatment plants.”
An immediate requirement
“This understanding [from the study] can help overcome this public health hazard because there are cheap ways to get rid of the arsenic from rice and water,” says Prof Benegal. He suggests a simple method to remove around 75 per cent of the arsenic from rice:
- Cook rice in boiling water.
- Midway through it, rinse the rice under running water.
- Continue cooking the rice without a lid, i.e., in an open pot.
Prof Benegal says efforts are also underway to develop microfilters that can remove metals like arsenic and iron from water. Bhalerao says a few companies are exploring reverse osmosis techniques to remove arsenic from water.
Editor’s note: This article is the second in a two-part series for the World Environment Day (5 June 2023)
