Silent killers

  • Contamination of drinking water by toxic metal ions can have disastrous consequences, including cancer
Silent killers

Apr 9, 2015-

The 380th episode of BBC Sajha Sawal (February 22) showed that there had been a tremendous rise in the number of patients with chronic diseases related to the heart and kidney in Nepal. Whether this increase is a result of the easy detection of diseases due to advancements in medical science and technology or if such ailments are actually on the rise, this does not bode well for the public.

Reports show that many in big cities are increasingly suffering from some kind of chronic disease these days. The number is slowly increasing in villages too. The causes are often a busy lifestyle, uncontrolled diets, a lack of physical exercise, stress, and contamination of food and drinking water. Some of these diseases, such as obesity, diabetes, stress, and high blood pressure, are often manageable and preventable through improved diets, exercise, early detection, and treatment. Therefore, there is a need for the government to prioritise the control of diseases that are caused by contaminated food and water and a polluted environment which, to a large extent, is beyond the control of a single person. This article will, therefore, focus on how toxic metal ions found in the environment can cause chronic diseases and how we can keep ourselves safe from these pollutants.

In the water

High population growth and poor supply and management have resulted in an acute water shortage in Kathmandu. Kathmandu Valley residents have already waited for 20 years for the much-vaunted Melamchi drinking water project and they are not certain how much longer they will have to wait. Out of 400 million litres of daily demand for water, Kathmandu Upatyaka Khanepani Limited is currently only able to supply 130 million litres. The demand for water is, therefore, largely met by private tankers and underground water from tube-wells or wells. There is no guarantee, however, if such water is drinkable.

According to the World Health Organisation (WHO) standard, drinking water should not contain any harmful chemicals, toxic metal ions such as arsenic, cadmium, lead, and mercury, and microorganisms. If present, they must not exceed certain parts per million (1mg/litre). It is uncertain whether drinking water in all of Nepal’s cities is tested for contamination, as many cities do not have essential equipment and laboratories to measure its quality. Water contaminated with toxic metals cannot be purified by boiling and filtration. The effects of such metals are seen only after a long time of exposure and therefore, they are sometime called ‘silent killers’. Toxic metals are ubiquitous environmental contaminants. Millions of people in South Asian countries are affected by arsenic poisoning through drinking ground water. WHO has estimated that one out of 10 deaths in Bangladesh could be from arsenic-triggered cancers.

Toxic metals can reach and contaminate water, soil, and air through industrial and vehicle smoke, waste chemical materials from hospitals, colleges, and schools, batteries, fluorescent light, paints, and plumbing materials. They can reach our blood through drinking water, air, fruits, vegetables, and other food products produced in such contaminated water/soil. Fish consumers have a very high probability of mercury toxicity because fish can store mercury about 100,000 times higher than the mercury found in water. The effect of toxic metals is more pronounced in fetuses and children younger than five years old. Therefore, physicians often suggest that pregnant women not include too much fish in their diet.

Could be cancerous

Toxic metal ions and their compounds are highly soluble in water. Water contaminated with such toxic metal ions is colourless, odourless, and tastes no different from clean water. Its level of toxicity can only be known after a test. Once they reach our bloodstream, owing to their high affinity with biomolecules, toxic metals displace the essential metal ions from protein, enzymes, and DNA. As a result, these biomolecules get poisoned, slow down, and eventually stop functioning. Furthermore, they produce very reactive oxygen species (ROS) inside cells, which kill protein and DNA. These ROS damage nerve tissue very easily, causing neurodegenerative diseases. Overproduction of ROS is also called oxidative stress. Studies have shown that oxidative stress can cause different types of cancers, Alzheimer’s, Parkinson’s, and heart- and kidney-related diseases.

Research published in Science journal in March 2013 shows that a special type of bacteria grown in the dark, in the depths of water and anaerobic conditions are able to convert toxic mercury to neurotoxic methyl-mercury. Drinking such water can result in a variety of neurodegenerative diseases. Cancers are caused due to abnormal growth of cells and there is no any single factor which results in the disease. Of the many factors, toxic metals could also cause cancers.

Steps forward

To prevent this, we need responsible waste management of harmful, carcinogenic, and toxic chemicals. Every one has a role to play. A step forward for the government would be to ban very old vehicles. The government can implement a smoke test for vehicles during registration or renewal every year. Bricks and cement factories that produce smoke and dust should be established away from residential areas. The government should guarantee pure drinking water and those who use underground water must have their water samples checked regularly to see if they contains any toxic metals. If the state lacks essential equipment and laboratories to quantify toxic material in water, the government should prioritise establishling an equipped laboratory.

We must be very careful with regards to waste management in hospital, college and school laboratories, and industries. The government can establish an Occupational Safety and Health Administration and Environmental Protection Agency to monitor and control waste management and ensure environmental protection.

On a personal level, thiol- and selenium-containing compounds found in garlic, leek, and onion can help remove toxic metals from the body. Fruits and vegetable are good sources of antioxidants such as polyphenol and vitamins that help destroy toxic ROS. Thus, consuming plenty of such food would be beneficial. This could be one way to prevent chronic diseases in case they are not genetically linked.

Neupane is a chemist and postdoctoral research associate at the Oak Ridge

National Laboratory, Tennessee, the US

Published: 09-04-2015 08:29

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