new delhi even though overall child mortality declined significantly in 1990s environmental hazards stilled kill three million underfive children annually a recent report has saidunderfive children made up roughly 10 per cent of the world population but comprised more than 40 per cent of the population suffering from environment related health problems washingtonbased ngo population reference bureau said in its report emerging policy issues in population health and environmentthough awareness and new regulatory standards had improved the situation for them in the developed countries children in less developed countries continued to be exposed to toxins the report saiddue to their size physiology and behaviour children were more vulnerable than adults to environmental hazards it said adding they were more heavily exposed to toxins in proportion to their body weight and had more years of life ahead of them in which they might suffer longterm effects from early exposureprenatal conditions which could be influenced by environmental conditions caused 20 per cent of deaths worldwide in children under five the report said adding fatal exposure to chemicals such as lead increases a childs chances of having brain damage or developmental problemsas children under five breathe more air drink more water and eat more food per unit of body weight than adults they may experience higher rates of exposure to pathogens and pollutants children between five and 18 years of age might face higher risks of injuries including exposure to hazardous chemicals due to their growing participation in household chores and work outside of home the prb report saidhalf the worlds households use biomass fuels including wood animal dung or crop residues that produces particulates carbon monoxide and other indoor pollutantsaccording to world health organisation who as many as one billion people mostly women and children are regularly exposed to levels of indoor pollution that are up to 100 times those considered acceptablein india where 80 per cent of households use biomass fuel estimates show that nearly 500000 women and children underfive die every year from indoor pollution largely from acute respiratory infections aris the report saidindoor pollution can cause or aggravate aris including upper respiratory infections such as cold and sore throats and lower respiratory infections such as pneumoniaacute lower respiratory infections were one of the primary causes of child mortality in developing countries and led to 22 million deaths in children under five it said adding aris could also increase mortality from measles malaria and other diseasesstudies in less developed countries had also linked indoor air pollution to lung cancer still births low birth weight heart ailments and chronic respiratory diseases including asthma the report saidthe disease caused 180000 deaths every year including 25000 childrens it added over 60 per cent of diseases associated with respiratory infections are linked to exposure to air and outdoor pollutants such as sulphur dioxide ozone nitrogen oxide carbon monoxide and volatile organic compounds come mainly from motor vehicle exhaust power plant emissions open burning of solid waste and construction related