Research tells us that dirty air is associated with problems in the lungs, heart, uterus and eyes, and might affect mental health. As well as shoes, it now appears that dirty air can also weaken our bones.
Ranzani and colleagues (2020) took readings of levels of PM2.5, a fine particulate form of pollution, at 23 sites outside Hyderabad in India.
Then they worked with more than 3,700 people in nearby villages to explore whether exposure to the air pollution was correlated with changes in the bone mineral content of their hips and spines, a measure of bone strength used to diagnose osteoporosis.
“What we see overall is a quite consistent pattern of lower bone mineral content with increasing levels of air pollution,” says Cathryn Tonne at the Barcelona Institute for Global Health in Spain.
People in the area were exposed to average annual PM2.5 levels of 32.8 micrograms per cubic metre – three times higher than the safe limit recognised by the World Health Organisation. After adjusting for other possible factors, including wealth, Tonne and her colleagues found that every extra 3 micrograms of PM2.5 per cubic metre was associated with an average reduction in bone mineral density for both men and women of 0.011 grams per square centimetre in the spine, and 0.004 g/cm2 in the hip. Black carbon, a subset of PM2.5, was also associated with lower bone mass.
More than half of the people in the study live in homes where food is cooked using solid biomass fuels, which release the pollutants. But no link to bone mass was found for those who used biomass as their main cooking fuel. This suggests it is the general exposure to air pollution in the ambient air that is responsible for the link.
Ranzani, O.T., Mila, C., Kulkarni, B., Kinra, S. & Tonne, C. (2020) Association of Ambient and Household Air Pollution With Bone Mineral Content Among Adults in Peri-urban South India. JAMA Network Open. 3(1):e1918504. doi:10.1001/jamanetworkopen.2019.18504.
Vaughan, A. (2020) Air Pollution May Weaken Our Bones. New Scientist. 11 January 2020. pp.8.