World Water Development Report, 2022 released by UNESCO, reveals that global use of freshwater has increased nearly eight times over the past hundred years and has been growing by about one per cent per annum since the 1980s. From the same report, we come to know that India’s water quality is poor ~ it ranks 120th among the 122 nations. Maintaining water quality conforming to the specifications prescribed by the Central Pollution Control Board (CPCB) has, therefore, become a challenging job, because unsafe water has severe implications for human health.

To begin with, one would like to know the magnitude and intensity of the impact of water pollution on human health for understanding its gravity. The type of diseases emanating from polluted water that affect human health can be broadly divided into three categories, namely, gastrointestinal diseases, skin diseases and cancer. Diarrhea is a common symptom of gastrointestinal diseases and the most common disease caused by water pollution.

The source of gastroenteritis, dysentery, diarrhea, and viral hepatitis is the water pollution due to coliform bacteria. Enteroviruses exist in the aquatic environment. More than hundred pathogenic viruses are excreted in human and animal excreta and spread in the environment through groundwater, estuarine water, seawater, rivers, sewage treatment plants, insufficiently treated water, drinking water, and private wells.

Skin disease is the most common clinical complication of arsenic poisoning and caused by water containing excessive arsenic, in other words above the threshold level. There is a correlation between arsenic concentration in biological samples from patients with skin diseases and intake of arsenic contaminated drinking water. Studies have shown that swimmers are about four times more likely to report skin diseases than non-swimmers. It has also been clinically proved that fall of hair is less for the people drinking low-arsenic content water.

Coming to the issue of cancer from the perspective of water sources, findings of seminal research studies reveal a high association of occurrence of cancer with presence of arsenic, nitrates and chromium in the drinking water consumed by patients.

Ingestion of arsenic from drinking water can cause not only skin cancer, but also kidney and bladder cancer. The risk of cancer in the population from arsenic may be comparable to the risk from tobacco smoking and radon in the home environment. However, individual susceptibility to the carcinogenic effects of arsenic varies. Studies have also shown a synergistic effect of smoking and intake of arsenic in drinking water in causing lung cancer. Exposure to high arsenic levels in drinking water is also associated with the development of liver cancer.

Nitrates are a broader contaminant that are more closely associated with human cancers, especially colorectal cancer. A study con?rmed a signi?cant association between colorectal cancer and nitrate in men, but not in women.

Intake of drinking water containing hexavalent chromium has the potential to cause human respiratory cancer. Presence of trihalomethane (THM) in drinking water causes bladder and brain cancers in both men and women. Kidney cancer in men is positively correlated with levels of THM content in drinking water.

The World Water Development Report lays bare the economic losses of waterborne diseases outbreak. According to the 2022 report, it is estimated that around 38 million Indians are affected by waterborne diseases annually. Nearly 1.5 million children under the age of five are estimated to die of diarrhea alone and 73 million working days are lost due to waterborne diseases each year. The economic costs of waterborne diseases are estimated at USD 600 million annually. Worldwide, child deaths constitute about thirty per cent of total deaths. Poor water quality, sanitation, and hygiene result in the loss of about 31 million disabilities-adjusted life years in India. The annual economic loss is estimated at around Rs 120 crore.

The World Health Organisation estimates that about ninety per cent of the waterborne diseases are attributable to unsafe water supply, sanitation and hygiene. Parasitic worms present in unpurified drinking water, when consumed by human beings, cause diseases.

Reports based on scientific studies reveal that treated water from water treatment facilities is associated with a lower risk of diarrhea than untreated water for all ages. Households without access to piped water have a five times higher risk of infant death from diarrhea than households with access to such water.

To sum up, it can be said that the impact of water pollution on different diseases is mainly reflected in the following aspects. Firstly, diarrhea is the most lethal water-borne disease, mainly transmitted by enterovirus existing in the aquatic environment.

The transmission environment of enterovirus depends on groundwater, river, seawater, sewage, drinking water, etc. Therefore, it is necessary to prevent the transmission of enterovirus from the environment to people through drinking water intervention.

Secondly, exposure to or use of water polluted with high levels of arsenic content, and heavy metals, is associated with a risk of skin diseases.

Thirdly, arsenic, nitrate, chromium, and trihalomethane are major carcinogens in water sources, which cause cancer.

Finally, water pollution is an important cause of children’s diseases. Contact with microbiologically infected water can cause diarrheal disease in children. Malnutrition and weakened immunity from diarrheal diseases can lead to other diseases.

In response to these research conclusions, countries, especially developing countries, need to adopt corresponding water management policies to reduce the harm caused by water pollution to human health. What steps need to be taken by the government?

Firstly, there should be a focus on water quality at the point of use, with interventions to improve water quality, including chlorination and safe storage, and provision of treated and clean water.

Secondly, in order to reduce the impact of water pollution on skin diseases, countries should conduct epidemiological studies on their own in order to formulate health-friendly bathing water quality standards suitable for their specific conditions.

Thirdly, in order to reduce the cancer caused by water pollution, the whole process of supervision of water quality should be strengthened; that would include the purity of water sources, the scientific nature of water treatment and the effectiveness of drinking water monitoring.

Fourthly, each society should prevent and control various sources of water pollution from production, consumption, and transportation.

Fifthly, health education should be widely carried out. A regular programme should be practiced for awareness of environmental issues and disposal of sanitary water in order to enhance public health awareness.

Besides, public health expenditure in India should be at least five per cent of its GDP. Farmers should also be trained to avoid overuse of agricultural chemicals that contaminate drinking water detrimental to human health.

(The writer is Director & CEO, Sayantan Consultants Pvt. Ltd., Kolkata)