Young students and their parents wearing masks walk along a street on a hazy day in Harbin, Heilongjiang province, China, November 3, 2015. Some kindergartens and schools were closed as severe air pollution hit northeastern Chinese city of Harbin on Tuesday, local media reported. China Stringer Network/Reuters An unhealthy environment was responsible for 12.6 million deaths in 2012, nearly one in four worldwide, according to a new report by the World Health Organisation (WHO).

The WHO report looked at how environmental risks such as air, water and soil pollution, chemical exposure, climate change and ultraviolet radiation, influenced diseases and injuries.

The report shows that deaths from infectious diseases mostly associated with water, sanitation and waste management have declined.

Noncommunicable diseases (NCDs) such as stroke, heart disease, cancers and chronic respiratory disease, now represent nearly two-thirds of the total deaths caused by unhealthy environments.

The report shows that unhealthy environments most adversely affected young children and older adults. The places most affected by environment-related diseases are South-East Asia and Western Pacific Regions where 7.3 million people died, mostly of air pollution related diseases.

Dr Maria Neira, WHO Director for the Department of Public Health, Environmental and Social Determinants of Health, said that countries needed to urgently invest in strategies to make environments more healthy.

“Such investments can significantly reduce the rising worldwide burden of cardiovascular and respiratory diseases, injuries, and cancers, and lead to immediate savings in healthcare costs," Neira said.

While Dr Margaret Chan, the WHO Director-General warned that if environments continued to be this unhealthy, millions would continue to fall ill. "If countries do not take actions to make environments where people live and work healthy, millions will continue to become ill and die too young," Chan said.

PCB contamination warning signs surround Silver Lake in Pittsfield, Mass., Friday, June 20, 1997. The old General Electric plant, left, is one of GE's 250-acre complex of plants in the northeast section of the city, where the contamination was thought to be concentrated, including a 55-mile stretch of the Housatonic River from the plant to the Connecticut border. Alan Solomon/AP The report emphasises how air pollution is becoming more and more of a threat and contributing environmental health factor. 8.2 million deaths due to NCDs in 2012 are attributable to air pollution according to the report.

Around 19% of all cancers, now a leading cause of death worldwide, were estimated by the WHO to be attributable to environmental factors.

Lung cancer, which killed 1.6 million people in 2012, is a prime example. Although smoking is the most important risk factor for the disease, "over 20 environmental and occupational agents are proven lung carcinogens in humans. Air pollution, for example from indoor burning of coal or biomass, was associated with substantial increases of lung cancer risk," the report says.

About 18% of all heart diseases worldwide were attributable to household air pollution and 24% to ambient air pollution. 42% of all strokes were linked to the environment.

The report says that the total environmental deaths did not change since 2002, but that noncommunicable diseases are now linked to more deaths than before.

"The last decade has seen a shift away from infectious, parasitic and nutritional diseases to NCDs, not only in terms of the environmental fraction but also the total burden," the report says. "This shift is mainly due to a global decline of infectious disease rates, and a reduction in the environmental risks causing infectious diseases, and a lower share of households using solid fuels for cooking."