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“We drink water but are always hesitant about the quality.” This seems to be miserable, that though we have plenty of water around, the supply of fresh potable water is still a heavy burden on our pockets (Vanloon and Duffy 2017). Being a key supportive system in daily livelihood and industrial development, ensuring the continuous supply of fresh water is an essential aspect. As per the United Nations Human Right Council (UNHRC), safe drinking water and sanitation are the fundamental right of every citizen for a sustainable healthy environment. The Council commits that by 2030 all people in the world should benefit from clean water assistance so as to allow equity for social and economic development. Such reforms and targets are already getting positive results in some developed countries but it seems that the situation is much more challenging for developing nations. In fact, it has been reported that developing countries like China, India, Sri Lanka, Egypt, Malaysia, Nigeria, Indonesia, Philippines, Bangladesh, etc. account for around 90% of debris disposed in oceans (Tran et al. 2020). Every day around two million tons of sewage and other waste get into water bodies, which corresponds to around eight million deaths every year where untreated water consumption is a direct cause (WHO, 14 May 2019).

Considering the water in the world, only ~2.5% is available as non‐saline freshwater but unfortunately, this is continuously undergoing contamination and thus a water crisis arises. From big quantities of garbage to some nano‐sized chemicals, a wide range of pollutants indulge in these water bodies and make them unfit for potable purposes. Along with these sources, the exploding population, lack of sustainable usage of water, climate change, rising industrial demand, farming and domestic sectors, and changing consumption patterns have also contributed in the freshwater crisis. It has been reported that water use has been increasing by about 1% per year since the 1980s and if this persists, then by 2050 an increase of ~20–30% above the current level of water use is expected (Islam and Karim 2019). Recently, the World Economic Forum in 2019 has categorized water pollution in one of the largest global risks due to human interventions (Băhnăreanu 2019). It has been reported that one‐sixth of the world’s population is suffering from freshwater unavailability (Elimelech 2006).

Water contamination could be natural or man‐made. Natural contaminants include geological materials from sedimentary rocks, floods, volcanic eruption, etc. with a wide range of elements like magnesium (Mg), calcium (Ca), copper (Cu), lead (Pb), iron (Fe), etc. These are essential for human health at some acceptable limits, but beyond that cause acute health effects (Vörösmarty et al. 2005; Ghrefat et al. 2014). Artificial contaminants include by‐products of petroleum, dyes, chemical, oil, batteries, and foodstuff industries. The Centres for Disease Control and Prevention reports Hepatitis A virus, norovirus, Escherichia coli, Salmonella, fluoride ions, heavy metals like As, Pb, Cd, Hg, Cr, Zn, perfluoroalkyl substances (PFAS), chlorinated solvents, pesticides, nitrates, and carbonates as the leading causes of these waterborne diseases (Cramer et al. 2008).

In addition, the use of pesticides, insecticides, and fertilizers in agricultural practices also add to this section (Kass et al. 2005). Pathogens and parasites, spread by human and animal waste, also pollute water to some extent; however, their proportion is comparatively less than natural and artificial contaminants.

Volatile organic compounds (VOCs) including chemicals like toluene, styrene, phosgene, gasoline additives, and adhesives, and microorganisms like Salmonella, Vibrio cholera, and Shigella, also contribute to chronic diseases like typhoid, fever, vomiting, diarrhoea, dysentery, gastroenteritis, and cholera (Council 2009; Soni et al. 2018).

Generally, water spoiled with pollutants causes different health problems to humans, plants, and aquatic life (which directly/indirectly affects humans). Exposure to these noxious wastes lead to chronic poisoning characterized by neurological, gastrointestinal, and cardiovascular problems, and liver damage (Dada et al. 2016).

Fluoride in water is essential for protection against bone weakening but concentration above 0.5 mg/L leads to fluorosis. Ingesting large quantities of Cu‐contaminated water causes diarrhoea, fever, liver, and kidney damage. Exposure to PFAS can lead to fertility problems, cholesterol rise, cancer, and thyroid problems. According to the Environmental Protection Agency, a person’s exposure to PFAS should be less than 70 parts per trillion and in Hoosick Falls, it was detected to be 1 30 000 parts per trillion (Michaels 2017).

Long‐term Cd exposure by consuming the food crops irrigated by effluents may cause kidney and skeletal damage (Friberg and Vahter 1983). Infants and pregnant ladies consuming Lead (Pb) contaminated water can experience developmental delay, abdominal pain, birth defects, hypertension, and preeclampsia. Pb contaminates in drinking water from pipes, solder, and household plumbing systems and affects the blood, central nervous system, and kidneys. Flint, Michigan, is an example in this regard. The city officials decided to start using Flint River as an alternative point water source for short period of time in 2014. The new water pipeline was built but not treated with any anti‐corrosive agent to deter Pb contamination. Studies revealed that this negligence led to increase in the blood lead levels by a factor of two, three, or more, which actually causes many skin‐related problems (Grossman and Slutsky 2017).

Metallic Hg is an allergen which may cause oral lichen and damage to the nervous system. The Minamata case is the best known example, where the Minamata Bay was contaminated by high content of Hg discharge. Around 2000 were poisoned; hundreds of deaths were reported from Minamata disease, which arises due to the consumption of fish containing methyl mercury (Mishima 1992). Intake of large quantities of arsenic (As) metal for long periods of time leads to haemolysis, melanosis, polyneuropathy, bone marrow depression, etc.

Accumulation of heavy metals also affects the aquatic flora and fauna and constitutes public health problem when contaminated species are used for food. It has been reported by World Health Organisation (WHO) in 2019 that transmitted diseases from polluted water like diarrhoea, pneumonia, typhoid, cholera, polio, etc. cause more than 4 85 000 deaths per year (WHO, 14 May 2019). Despite affecting human health, water pollution also has an adverse effect on plants. Nutrient deficiency in water ecosystem, excess use of agricultural chemicals, etc. hinders plant growth and also poisons the plant.

Though we have made technological advancements in the previous decades, the lack of sustainable usage and pretreatment solutions have made thousands of rural towns unavailable of safe potable water. As per the WHO report, two million people received groundwater comprising contaminants like arsenic, radium, and fluoride ions. It is not surprising that thousands of communities could not afford to filter these pollutants off and intake the same polluted water (Shannon et al. 2010). Here, it should be mentioned that heavy metal sources are the major source in water deterioration.

The chapter discusses all the above mentioned aspects and is divided in sections. The first section addresses the general introduction of water quality. The second section emphasizes the different sources of the major pollutant, i.e. heavy metal contamination in groundwater for detailed study. The third part of this chapter contributes to the type of pollution. This section emphasizes heavy metal pollution. In the fourth section, we have discussed the effect of heavy metal pollution on human body. The fifth and sixth sections throw light on recent strategies to control water pollution and remediation of heavy metals. We have discussed the future strategies adopted by different governments and suggest some measures to remove these exudates in the water. At last, this chapter ends with future expects and conclusions drawn.