The good news is that more people have mosquito nets, and better access to clean water and toilets. The bad news, says Dr Maria Neira, head of public health and the environment for the World Health Organisation (WHO), is that populations have grown fast and little progress has been made in the past 10 years to prevent illness in developing countries.

“Yes, we are spending more on treating TB, malaria and diarrhoea than we were 10 years ago. But we are not spending anything like enough on building good sanitation and water systems. Only 3% of our health spending goes to stop people becoming sick; 97% is spent when people are sick.”

The global disease figures, released last week in a major WHO report, are stark, says Neira. The environment now contributes to more than 100 of the most dangerous diseases and kills 12.6 million people a year – nearly one in four of all deaths. One in five cancers are linked to environmental causes, as are one in four strokes. The number of people dying from poisonous air in burgeoning cities is rising fast.



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Most of these environmental diseases are entirely preventable, according to Neira. “We have failed in the last 10 years to help developing countries avoid making mistakes in cities; we have failed to help them avoid congestion and air pollution, and we have failed dramatically to increase the number of people using clean cooking stoves,” she says.



The report, conducted once a decade to show broad health trends, identifies a significant shift from deaths caused by infectious, parasitic and nutritional diseases to non-communicable diseases (NCDs) including strokes, cancers and heart illness, which are linked to sedentary lifestyles, cities and pollution.

“This shift is mainly due to a global decline of infectious disease rates, and a reduction in the environmental risks causing infectious diseases – a higher share of people having access to safe water and sanitation, and a lower share of households using solid fuels for cooking,” explains the report.



But, says the WHO, 23% of all deaths and 26% among children under five are still due to modifiable environmental factors. Heading this list are stroke, heart disease, diarrhoea and cancers. “This environmentally mediated disease burden is much higher in lower-income countries, with the exception of certain NCDs, like cardiovascular diseases and cancers, where the per capita disease burden is greater in the developed world.”

Facebook Twitter Pinterest A child diagnosed with having excessive lead in his blood receives treatment at a hospital in Chenzhou, China. Photograph: Kevin Zhao/Reuters

Of the 12.6m deaths now caused by poor management of people’s environments, 8.2m are from NCDs.



For low- and middle-income countries, says Neira, this shift to chronic diseases, which last for a long time and progress slowly, will shape national approaches to health for years to come.



“Until now we were focusing on communicable diseases, like dengue, TB, even Zika. The key message now is that we are talking about diseases like strokes, cancers and heart illnesses.

“Communicable diseases are largely the same as 10 years ago, but population has increased. They are still the main problem, but NCDs are much more costly because they require long-term attention and more hospitalisation,” she says.

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Air pollution in developing countries has become a major public health issue. “We have 3.7 million people dying a year from outdoor air pollution, and 4.3 million from household pollution. Almost half the world is still cooking like in the stone age.

“For many years [everyone talked ] about access to clean water. But now we realise access to clean air is also fundamental to health. Ambient air pollution is getting worse. In the past we were thinking this only led to respiratory diseases. Now we know air pollution gets into the bloodstream and leads to strokes and heart diseases. That is a big shift. When we have 7m deaths a year, then it’s a major public health issue.”



Developing countries, she says, must act now to avoid a catastrophic decline in health as they urbanise and become more prone to diseases that are linked to sedentary lifestyles.

“We are are creating a situation where millions are dying, creating environments that are responsible for one-quarter of all deaths. All these 12m deaths from unhealthy environments are preventable, and most are in the poorest countries.

“We must understand that health is linked to how we live as much as [to] how much we expose ourselves to risk. Health is coming from the type of agriculture we do, the type of pesticide we use, the food we eat, the type of transport we use in daily life. It’s about living in places where we can walk, and do not develop diseases like diabetes. It’s about changing our consumption patterns, energy saving and sanitation.”



All investment needs to be directed very strategically to preventing environmental disease, adds Neira. “Air pollution, access to clean water and sanitation, and the planning of cities are key to all future development.

“Health needs to go into every equation for development. If we take the wrong choices now, our health will be devastated in terms of death, lack of quality of life and economic costs.”