A report prepared by three United Nations agencies concludes that about 5,500 children die each day around the world from diseases caused by environmental pollution. The report, "Children in the New Millennium: Environmental Impact on Health" was prepared by UNICEF, United Nations Environment Programme and the World Health Organisation. Environmental contamination gives rise to a number of diseases, including diarrhea and acute respiratory infections —two of the leading causes of child mortality. According to Carol Bellamy, Executive Director of UNICEF: "We have made great strides over the last decade, children are healthier today, there is more access to clean water, but these disturbing figures show we have barely started to address some of the main problems.

The report identifies a number of environmental problems that directly affect the children, such as toxic chemicals and depletion of natural resources. For example, most of the lead in the environment comes from leaded petrol and it causes anaemia, permanent neurological and developmental disorders in children. It has also been found to be correlated to subnormal intelligence. During 1997, a study was conducted by the All India Institute of Medical Sciences, New Delhi, to find the blood lead level among school-going children in Delhi. Blood samples were collected from 200 children from Siri Fort and Daryaganj areas of Delhi. It was observed that the blood lead levels among 56 per cent of children in Siri Fort area and 72 per cent in Daryaganj had elevated blood lead levels.

Children working in agricultural fields often come in contact with pesticides. Children are also vulnerable to global environmental problems such as global warming, stratospheric ozone depletion and destruction of biodiversity. As per the WHO estimates, almost one-third of the global disease burden can be attributed to environmental risk factors. More than 40 per cent of this burden falls on children under five years of age, even though they account for just 10 percent of the world’s population.

A major contributing factor to these diseases is malnutrition, which affects around 150 million children and affects their immune system. Malnutrition and diarrhea form a vicious cycle. The organisms that cause diarrhea harm the walls of the digestive tract, which prevents them absorbing their food, causing even greater malnutrition and vulnerability to disease.

During the International Conference on Environmental Threats to the Health of Children, held at Bangkok in March 2002, a WHO release revealed that three million children under the age of five die each year due to environmental hazards. Children are not little adults, since they are still growing and their immune systems and detoxification mechanisms are not fully developed. They are specially vulnerable to chemical, physical and biological hazards in air, water and soil. "A commitment to child health means that hazards should be reduced in all places where children spend significant parts of their day, including the roads and forms of transport they use to get to and from these places" said Richard Helmer, Director of WHO’s department responsible for environmental health.

As much as 1.3 million children under five in developing countries died from diarrhoel diseases caused by unsafe water supply, sanitation and hygiene in the year 2000. Hundreds of thousands of children die from acute respiratory infections associated with indoor air pollution from the burning of biomass fuels in small, confined spaces and other insanitary living conditions. Accidental injuries—including road traffic accidents, drowning, burns and poisoning—are the cause of over 400,000 deaths a year in children under five.

A report brought out by the National Resources Defence Council, a US based NGO, points out that children who ride on diesel school buses may be exposed to dangerously high levels of toxic diesel fumes inside the vehicle. Using sophisticated equipment to continuously sample the air inside the buses, the team of researchers compared air quality inside the front and back of the buses, with the windows both open and closed. Diesel exhaust is known to be a major source of fine particles that can lodge deep in the lungs and worsen asthma, a condition most prevalent among children. In addition, smog-forming oxides of nitrogen which also are emitted from diesel engines in large quantities, have recently been linked to decreased lung function growth in children. The report found that children who ride diesel school buses may be exposed to as much as four times more toxic diesel exhaust than people riding in vehicles travelling behind or in front of such buses. The exposure level on the buses is more than eight times the average ambient air pollution level, and as much as 46 times the diesel fumes cancer risk exposure threshold established by the U. S. Environmental Protection Agency.