From dengue fever to depression, we look at the health risks from climate change
By Megan Darby
The things we need to be healthy – food, water, shelter and fresh air – are all affected by climate change.
And while global warming may mean fewer cold-related deaths in some parts of the world, it is also set to spread exotic diseases to new areas.
A major study in the Lancet described climate change as “the biggest global health threat of the 21st century”.
The World Health Organization is hosting a global conference on the links between climate change and health later this week.
In the first of a series of articles on health, RTCC looks at some of the ways our changing climate is hurting health.
1. Rise of the bloodsuckers
Climate change can alter the breeding seasons and geographical range of mosquitoes, ticks and even snails that carry diseases.
Malaria, spread by mosquito bites, kills around 1 million people a year, mainly under-5s in Africa. Economic development and health initiatives have helped reduce the number of people infected.
But researchers at the London School of Hygiene and Tropical Medicine have warned rising temperatures could push the disease into mountainous areas, where people do not have protective immunity.
Dengue fever, the most rapidly spreading mosquito-borne virus, is also getting into new territory. According to the IPCC, infections have risen 30-fold in the last half century to 390 million a year and another 2 billion could be exposed by 2080.
A study from the University of East Anglia last week found the disease, which causes fever, headaches, muscle and joint pain, could become established in southern Europe.
Tick-borne encephalitis, chikungunya fever and plague – yes, plague – are also sensitive to climate. And schistosomiasis, a disease carried by snails, is expected to spread to a larger area of China.
2. Air pollution and allergens
Air pollution is responsible for one death in eight worldwide, the WHO estimates. It killed 7 million people in 2012.
Maria Neira, WHO director of public health, said: “Few risks have a greater impact on global health today than air pollution; the evidence signals the need for concerted action to clean up the air we all breathe.”
Climate change is set to spark more wildfires, which cause acute air pollution.
Meanwhile, warmer conditions lead to the release of air-borne allergens that trigger asthma and other conditions such as rhinitis, conjunctivitis and dermatitis.
Some 300 million people worldwide suffer from asthma, which in severe conditions can kill as the body struggles to get oxygen.
On hot days, more people die. These can be young people getting heatstroke from over-exertion or the elderly and chronically ill.
When body temperature rises above 38C, it puts a strain on the heart, lungs and kidneys.
High temperatures also raise levels of ozone and other pollutants, which are damaging to health.
And trying to avoid heatstroke can hit productivity, as farmers and construction workers need to take longer breaks.
With climate change, extreme weather such as drought, flood and hurricane is set to become more common.
Such events can put a strain on the mental health of survivors. They may have lost loved ones and property or had to leave their homes.
Symptoms of anxiety and depression are two to five times more prevalent among people who have experienced flooding in their home than the general population.
After Hurricane Katrina in the US, signs of mental illness related to the disaster were still seen two years later.
Rising temperatures and changing weather patterns will hit food production in much of the world while populations grow.
In some African countries, yields of staple food crops are expected to fall as much as 50% by 2020.
This will exacerbate malnutrition, which already kills 3.5 million people a year.
According to the International Food Policy Research Institute (IFPRI) 25 million more children will be malnourished in 2050 due to the effects of climate change.
“The impact of climate change on access to food is huge,” according to Natasha Adams of UNICEF.
6. Skin cancer
Man-made gases first caused a hole in the ozone layer, which lets through more UV radiation and increases the risk of skin cancer.
While a global treaty has cracked down on the ozone-depleting substances, Harvard researchers have found climate change may worsen the ozone problem.
“If you were to ask me where this fits into the spectrum of things I worry about, right now it’s at the top of the list,” said lead author James Anderson.
There have been suggestions that thawing graveyards in the Siberian tundra could bring back smallpox, a virulent disease that was officially eradicated in 1980.
The virus could be transmitted from the frozen corpses of smallpox victims, under this nightmare scenario.
Kevin Brown, lead clinical virologist for Public Health England reassured MailOnline: “Although short lengths of smallpox viral DNA has been detected in corpses in the permafrost in Siberia and other preserved historical artefacts, no infectious virus has ever been obtained from archaeological remains.
“There is no evidence that previously frozen corpses in the permafrost are a potential source of infectious smallpox virus.”