Ninety-one per cent of schools in Delhi were located within five kilometres of a documented toxic site, the highest proportion among the ten capital cities studied across the developing world, according to a new working paper from the Center for Global Development (CGD), a Washington and London-based research organisation.

The report matched the locations of 2.6 million schools across 17 low- and middle-income countries to 11,301 documented sites contaminated by lead, arsenic, cadmium, mercury and other pollutants, and measured how close schools sat to them.

Delhi’s 91.2% proximity rate placed it well above every other capital in the study. 

Metro Manila (the Philippines) followed at 86%, Nairobi (Kenya) at 71.9%, Greater Accra (Ghana) at 67.6%, Bogota (Colombia) at 55.4%, Jakarta (Indonesia) at 51.8%, Buenos Aires (Argentina) at 46.1% and Lima (Peru) at 38.4%. 

Mexico City (Mexico) stood apart from the rest, with virtually no school within five kilometres of a catalogued site, since the country’s contaminated land was concentrated in industrial corridors well outside the capital.

The report noted that “capital cities concentrate exposure dramatically”, with nine of the ten capitals showing proximity rates far above their national averages. 

Delhi versus the rest of India 

In Delhi’s case, the gap was stark. While 91% of the capital’s schools sat close to a toxic site, the all-India figure stood at just 4.7%, since the national count included hundreds of thousands of rural schools spread across a vast country with comparatively few documented sites outside its cities. 

Chandigarh came second among Indian states and union territories at 75.4%, followed by Punjab and Gujarat at around 11% each.

Nationally, India had 668 sites listed in Pure Earth’s Toxic Sites Identification Program and a further 105 in the Central Pollution Control Board’s own contaminated site register, together forming the base for the country’s proximity estimates. 

Lead accounted for 321 of the 668 sites tracked in India, making it the most common contaminant, largely linked to informal battery recycling, smelting and industrial waste handling. 

Weighted by enrollment, the report estimated that 21.8 million Indian children attended a school within five kilometres of a documented site, with 2.8 million attending school within one kilometre.

The paper found that exposure in India, as in the other countries studied, followed a clear pattern. 

Urban schools were far more likely to sit near contaminated land than rural ones, at 20.6% against 2%, which is a tenfold gap. Within cities, the pattern also tracked family income. 

Schools in India’s wealthiest neighbourhoods were found to be about 39.2 times more likely to sit near a documented site than schools in the poorest neighbourhoods, one of the steepest such gaps recorded in the study. 

The report explained this was because “industry and schools concentrate in wealthier urban cores in LMICs” rather than being pushed to the margins as tends to happen in wealthier countries. Private schools in India were also found to be more exposed than government schools, at 10.5% against 3%.

Proximity is not proof of harm

The report was careful to describe its findings as measuring distance rather than confirmed harm. It stated that, “We measure proximity, not exposure or health impacts. Proximity is a necessary but not sufficient condition for exposure, which also depends on transport pathways, dose, and individual susceptibility; our estimates identify schools that warrant further environmental investigation, not confirmed cases of harm.” It further added that its estimates identified schools that “warrant further environmental investigation, not confirmed cases of harm.” 

The report also flagged that the true number of contaminated sites was almost certainly undercounted, since existing databases capture only a fraction of pollution sources on the ground, particularly in countries with limited environmental monitoring systems.

Even so, the report pointed to a substantial body of research linking pollution exposure to poorer learning outcomes in children. 

It cited studies from India, Brazil and Colombia showing that air pollution reduced test scores, and separate research from Mexico, Kenya and Indonesia linking lead exposure to lower cognitive performance. Childhood lead exposure alone was estimated elsewhere to cost developing countries close to a trillion dollars a year in lost productivity, since even low-level exposure could affect memory, learning and behaviour in children.

Globally, the study found that 9.7% of all 2.6 million schools examined lay within five kilometres of a documented toxic site, rising to 12.7% of students when weighted by enrollment across the seven countries with such data. 

Brazil’s Sao Paulo state, Armenia and Mongolia recorded the highest overall national proximity rates, while India’s countrywide figure was among the lowest, a reflection more of patchy record-keeping outside its major cities than the actual scale of contamination.

The report recommended that governments consider environmental screening before constructing new schools in urban areas, along with soil, water and air testing at schools already located near known contaminated sites. It also called for more comprehensive national inventories of polluted land, noting that better documentation, not necessarily worse pollution, often explained why some cities and countries appeared more exposed than others in the data.

Also read: Why Delhi’s toxic air can be dangerous for children’s lungs