Pollutants threaten health

Each year, thousands of Londoners die prematurely as a result of air pollution across the capital, and millions more face health threats every day. The city has breached legal limits for air quality every year since implementing them in 2010, and all of London’s boroughs fail both annual targets and World Health Organisation standards.

Although children and poorer communities are often the most vulnerable to the dangers of pollution, it impacts the entire city, costing the London economy an estimated £3.7 billion every year. People vulnerable to adverse health outcomes from exposure to air pollution include children, the elderly, minority and low-income communities, and those with diabetes, heart disease or respiratory problems. These groups may suffer an increased risk of developing cardiovascular disease, cancer, asthma and other respiratory diseases; or of worsening conditions that are already present.

What we typically think of as air pollution is actually a mixture of small particles such as black carbon, gases like nitrogen oxides, ozone, and sulphur dioxide.

Particulate matter (PM₁₀, PM₂.₅)

Particulate matter (PM) is made up of small airborne particles like dust, soot, and drops of liquids. Most PM in urban areas is formed from fossil fuels used in power plants, vehicles, construction equipment, and industrial facilities.

Coarse particulate matter (PM₁₀, particles smaller than 10 microns in diameter) is linked to nasal and upper respiratory problems. Fine and ultra-fine particles (PM₂.₅, particles smaller than 2.5 microns) penetrate deeper into the lungs and is linked to lung disease, heart attacks, strokes, asthma and cancer. Studies also show that PM₂.₅ exposure can impair childhood brain development. Long-term exposure to these particulates is linked to increased risk of heart disease and lung cancer, and a shorter life span. Short-term exposure can further exacerbate acute health effects and increase mortality rates.

While thresholds for PM have been set as general guidelines, there is little evidence to suggest a safe threshold below which there are no adverse health effects of PM.

Black Carbon (BC)

Black carbon is a component of particulate matter from combustion (especially diesel and wood). Populations with higher exposures to black carbon over a long period are at a greater risk of heart attacks and stroke. Black carbon is also associated with hypertension, asthma, chronic obstructive pulmonary disease (COPD), bronchitis, and a variety of types of cancer.

Nitrogen Oxides (NO and NO2)

Nitrogen oxide (NO) and nitrogen dioxide (NO₂) are produced primarily by the transportation sector. NO is rapidly converted to NO₂ in sunlight. NOx (a combination of NO and NO₂) is formed in high concentrations around roadways, and can result in development and exacerbations of asthma, bronchitis, as well as a higher risk of heart disease.

According to the World Health Organisation, long-term exposure to NO₂ can worsen bronchitis in asthmatic children and adversely impact lung function. In the short-term, exposure to NO₂ has been linked to acute health effects, including inflammation of the airways.

Ozone (O₃)

Ozone high up in the atmosphere can protect us from ultraviolet radiation, but at ground level (where it is one component of smog) it is a major respiratory irritant. It is formed through reactions of volatile organic compounds and nitrogen oxides, both of which come from fossil fuels. Short-term exposure to ozone can cause chest pain, coughing, throat irritation, while long-term exposure can lead to decreased lung function and cause chronic obstructive pulmonary disease (COPD). In addition, ozone exposure can aggravate existing lung diseases.

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