Environmental pollutants are killing millions of young children around the world.
According to two new reports from the World Health Organization, 1 in 4 deaths among children under the age of 5 can be linked to environmental hazards. That's 1.7 million deaths every year.
These hazards include unsafe water, lack of sanitation, indoor and outdoor pollution, secondhand smoke and inadequate hygiene.
Officials say such unhealthy environments can lead to fatal cases of malaria, diarrhea and pneumonia.
As WHO's director-general said in a statement: "A polluted environment is a deadly one — particularly for young children. Their developing organs and immune systems, and smaller bodies and airways, make them especially vulnerable to dirty air and water."
The studies' authors agree that air pollution is the biggest problem.
A separate report conducted by the United Nations Children's Fund last year found that nearly 600,000 children under the age of 5 die every year from diseases caused by air pollution.
Experts warn these child deaths will only continue to increase if we don't reduce these environmental risks.