THE British Medical Association (BMA) has said that climate change and air pollution are already damaging health – outdoor air pollution kills an estimated 40,000 people in the UK alone every year.
And the World Health Organisation (WHO) stresses that air pollution and climate change are intertwined – for example, the shifts in weather patterns due to climate change can cause more ozone to be produced at ground level, which harms our health. Increased ozone levels then contribute to more warming.
"Climate change and air pollution are among the most serious health challenges we face this century," says BMA board of science chair Professor Dame Parveen Kumar. "We need to see bold and immediate action if we are to curb this dangerous threat."
But exactly how are climate change and air pollution damaging our health?
Here the Royal College of Physicians and the Royal College of Paediatrics and Child Health outline 11 of the major health effects, as detailed in their Every Breath We Take: The lifelong impact of air pollution report.
1. Premature birth and stillbirth
When pregnant women breathe in some pollutants, including particulates and heavy metals, they can cross the placenta to the developing baby. Air pollution can affect growth of the unborn baby and may be linked to premature birth, which in some cases can lead to severe disability and early death.
From the earliest stages of development, DNA is susceptible to changes arising from exposure to air pollution, and even seemingly trivial interference during critical development periods can irreversibly harm a baby's organs and tissues.
Evidence also suggests potential links with higher rates of stillbirth. In addition, it is thought the exposure of pregnant women to traffic-related air pollution accounts for more than a fifth of all cases of low birth weight at term.
2. ADHD and low IQ
Children are especially vulnerable to air pollution, and may suffer permanent health impacts from early exposure. Heavy metals, particularly lead and mercury, which can cross the placenta and accumulate in the foetus, have been associated with neurodevelopmental harm, leading to reduced cognitive function, lower IQ, attention deficit hyperactivity disorder (ADHD), and possibly autism spectrum disorder during childhood.
3. Asthma and childhood respiratory illnesses
There's "compelling evidence" in children and adults that air pollution exposure is associated with new onset asthma. In the Californian Children's Health Study, exposure to higher levels of nitrogen oxides was associated with new-onset asthma, and children living within 75m of a major road had a 29 per cent increased risk of lifetime asthma. Plus, traffic-related air pollutants near the home and school were associated with a 1.5-fold-increased risk of new-onset asthma.
And as well as causing asthma, pollen and other aeroallergen levels are also higher in extreme heat, often caused by global warming. Such high aeroallergens can trigger asthma attacks.
In addition, children living in highly polluted areas are four times more likely to have reduced lung function in adulthood. Infants living in areas with high levels of particulate air pollution are at increased risk of death during the first year of life, particularly from respiratory illnesses.
4. Cardiovascular disease
Studies have shown significant associations between air pollution and a range of cardiovascular problems in adults. Both short and long-term exposure to air pollution can increase the risk of heart attacks, heart failure, arrhythmias (abnormal heart rhythms) and stroke in at-risk individuals, such as older people or those with pre-existing medical conditions. Once people have a heart condition, spikes in air pollution can make their symptoms worse, leading to more hospital admissions and deaths.
5. Cancer
The International Agency for Research on Cancer (IARC) classifies outdoor air pollution and particulate matter from it as carcinogenic to humans. It says there's strong evidence that exposure to outdoor air pollution is associated with changes in gene expression and genetic damage, which are linked to increased cancer risk. In addition, IARC says there's "sufficient evidence that exposure to outdoor air pollution causes lung cancer".
6. Obesity
Research suggests some air pollution may be connected to the development of obesity. Prenatal exposure to endocrine-disrupting chemicals, for example, has been reported to increase children's risk of obesity. Being overweight can also make people more vulnerable to the harmful effects of air pollution, while a diet rich in antioxidant nutrients, or which includes vitamin and mineral supplements, may give some protection.
7. Chronic obstructive pulmonary disease (COPD)
There's strong evidence that long-term exposure to outdoor air pollution suppresses normal lung function growth in children, and accelerates lung function decline in adults. COPD is common in the elderly, and is often linked to smoking. Patients with COPD have a reduced ability to clear inhaled material from their lungs and may, as a result, get a higher-than-normal dose of air pollution. So when air pollution is high, people with COPD have a greater fall in lung function and a higher risk of admission to hospital.
8. Dementia
The Alzheimer's Society says the most convincing evidence linking air pollution to dementia comes from a 2016 study of 6.6 million people from Canada. It found those living within 50m of a major road were 7 per cent more likely to develop dementia than people living more than 300m away, where fine particulate matter levels can be up to 10 times lower.
As there are other factors associated with living on a busy road, such as high noise pollution and stress, the Alzheimer's Society points out that the study doesn't prove air pollution causes dementia.
"However, it does suggest that the study of air pollution and dementia should be prioritised for future research," it adds.
9. Diabetes
There is "concerning" evidence that exposure to air pollution is associated with new-onset type 2 diabetes in adults. One study found living within 50m of a major road, compared with those living more than 200m away, was associated with new-onset type 2 diabetes.
10. Mental health
More frequent and severe flooding is a result of climate change, and health experts are concerned about the effect on people's mental health, with victims of the 2007 UK floods up to five times more likely to experience symptoms of stress and anxiety.
11. Spread of disease
Changes in climate are likely to alter the geographic range of serious vector-borne diseases (which are transmitted to humans and other animals by arthropods like mosquitoes, ticks, and fleas) like malaria and dengue.
