The Water Divide

1.4 million

deaths a year linked to unsafe water, sanitation and hygiene¹

2.2 billion

people without safely managed drinking water²

Up to 7

IQ points lost as a child’s blood lead rises³

1. The death divide

Put deaths from unsafe water and sanitation on a world map and one region lights up. In World Bank and WHO figures, the rate runs from under 1 death per 100,000 people in the best-served countries to more than 100 in the worst. Almost all of the darkest countries are in sub-Saharan Africa, with India and its neighbours close behind.

Behind that map are children. About 1 in 14 children in sub-Saharan Africa dies before turning five, compared with roughly 1 in 200 in Europe and North America⁴. Diarrhoeal disease, spread mostly through faecally contaminated water and poor sanitation, kills around 440,000 children under five every year⁵. It is preventable, and it is no longer a problem in wealthy countries.

A child’s chance of reaching five still depends on where they were born, and much of that gap is about water.

Water isn’t the only reason for the gap. Poverty, nutrition and access to clinics all play a part, and a map can’t pull them apart. But the countries where water makes people sick are, again and again, the same countries where young children die.

2. Lead: the quiet thief of IQ

Lead doesn’t make a child visibly ill at the levels most children meet. It works slowly and silently on the developing brain. The largest pooled study, covering seven birth cohorts, found that IQ falls fastest at the lowest exposures. Children lost about 3.9 IQ points as blood lead rose from 2.4 to 10 µg/dL, and about 6.9 points by 30 µg/dL³.

IQ is only part of the damage. The US Centers for Disease Control and Prevention lists learning and behaviour problems, slowed growth and development, and hearing and speech problems among the effects of childhood lead exposure⁶. The WHO is blunt: there is no known safe level of lead in the body⁷.

It isn’t just poor countries

• Flint, Michigan. After the city switched water source in 2014, the share of children with elevated blood lead roughly doubled, from 2.4% to 4.9%. Children outside the city saw no such rise⁸.
• Detroit. Detroit has long had some of Michigan’s highest rates of lead poisoning in children. Most of it comes from old paint and dust in pre-1978 housing, but lead service lines add to the risk⁹.
• New York City. Old paint is the main source here too. When the city tested drinking fountains and taps in its public schools, it found outlets above the federal lead action level and took them out of service¹⁰.
• Across the US. About 9 million lead service lines still carry water into homes. A 2024 federal rule requires most of them to be replaced within a decade¹¹.

3. Nigeria: bacteria and lead in the same glass

Search Lagos on Water Water and the report lists two substances documented at national level: faecal bacteria and lead.

Nigeria’s national household survey tests drinking water at the point of use, and E. coli turns up in a large share of household water¹². That means sewage is getting into what families drink. It puts Nigeria among the darkest countries on the death-divide map.

Lead has already caused one of the world’s worst poisoning disasters. In 2010, villagers in Zamfara State crushed lead-rich ore to extract gold. Lead dust contaminated homes, soil and water, and hundreds of young children died before treatment and clean-up began¹³. Survivors were left at risk of lasting brain damage.

The combination is what makes Nigeria stand out. Bacteria kill children quickly, and lead harms those who survive slowly. Families face both at once, and there is very little local data to warn them.

4. India and the region

South Asia holds nearly every kind of contamination in our index:

• Arsenic in groundwater along the Ganga and Brahmaputra, from Bihar and West Bengal to Bangladesh. Researchers estimate 50–60 million people in Pakistan’s Indus plain may drink high-arsenic water¹⁴. Long-term exposure causes skin lesions and cancers of the skin, bladder and lung.
• Fluoride above safe limits in groundwater across many Indian states, especially Rajasthan, where it can cripple bones and joints.
• Uranium above WHO guidance in groundwater across north-west India, including Punjab¹⁵.
• Sewage. Rivers like the Yamuna in Delhi carry heavy loads of untreated waste before the water ever reaches a treatment plant.

Most of these contaminants are colourless, tasteless and odourless. A family can drink from the same tube well for years without knowing.

5. Why nobody talks about it

Water contamination rarely makes the news, for four reasons:

1. It’s invisible. Lead, arsenic and bacteria don’t change how water looks or tastes.
2. It’s slow. Lost IQ points or a cancer twenty years later never show up as a single dramatic event.
3. It hits the least powerful hardest. Poor communities, old housing and informal settlements carry most of the burden.
4. The data is missing. Where testing is rare, the problem isn’t officially counted. When our map says “no research indexed”, that is the reason. It doesn’t mean the water is safe.

6. What you can do

• Check your area on Water Water to see what research has found near you.
• Test, don’t guess. Ask your water provider for its latest quality report, or use a certified lab, especially if you have young children or are pregnant.
• Treat for the right thing. Boil for germs. For lead, arsenic, nitrate or fluoride, use reverse osmosis or a filter certified for that contaminant.
• Run the tap. In older buildings, let cold water run before drinking, and never use hot tap water for baby formula.
• Talk about it. Share your report. Water problems persist because they are ignored.