More than one in four deaths in children under five is linked to polluted environments, according to two new World Health Organization reports published Monday.
Each year, environmental risks such as indoor and outdoor pollution, second-hand smoke, unsafe water and poor sanitation kill around 1.7 million children between the ages of one month and five years, the reports found.
Harmful exposure can start in the mother's womb, increasing the risk of premature birth, which can lead to life-long health problems.
When children are exposed to air pollutants they also can face a lifelong increased risk of chronic respiratory diseases, like asthma, and of heart disease, stroke and cancer.
The findings were in line with a WHO study published last year showing that about a quarter of all deaths worldwide, across all age groups, were attributable to environmental factors like air, water and soil pollution, as well as unsafe roads and workplace stress.
But the new reports highlight the particular dangers faced by the youngest in society.
"A polluted environment is a deadly one, particularly for young children," WHO chief Margaret Chan said in a statement.
"Their developing organs and immune systems, and smaller bodies and airways, make them especially vulnerable to dirty air and water," she said.
Reducing Environmental Risks
An estimated 570,000 children under five die each year from respiratory infections such as pneumonia, which are attributable to air pollution and second-hand smoke, the reports found.
And 361,000 others are killed by diarrhoea resulting from poor access to clean water, sanitation and hygiene, the agency said.
Another 200,000 children under five die from unintentional injuries linked to unhealthy environments, including poisonings, falls and drowning, WHO said.
The agency emphasised that a large portion of deaths among children stemming from common causes like diarrhoea, malaria and pneumonia could be prevented by reducing environmental risks.
Simply increasing access to safe water and clean cooking fuels, removing unsafe building materials like lead paint, and reducing the use of hazardous pesticides and chemicals could go a long way in preventing such deaths, the reports said.
A full 200,000 deaths each year among children under five due to malaria, for example, could be avoided through actions like reducing breeding sites for mosquitos and covering drinking water storage, the WHO said.
At the same time, a range of new environmental hazards are emerging, like the ballooning piles of discarded mobile phones and other electronic and electrical waste, which is expected to hit 50 million metric tonnes globally by next year.
When not properly recycled, such waste can expose children to toxins that can lead to reduced intelligence, attention disorders, lung damage and cancer, the WHO warned.
Climate change is also taking its toll on children, the reports found.
Rising levels of carbon dioxide contributes to pollen growth, which in turn is leading to rising rates of asthma in young people, the agency said.