New York, Feb 22 (IANS): Long-term exposure to air pollutants may lead to bone damage among postmenopausal women, finds a study.

Scientists from Columbia University in the US found that the effects were most evident on the lumbar spine, with nitrous oxides twice as damaging to the area as in normal ageing.

Car and truck exhaust is a major source of nitrous oxides, as are the emissions from electrical power generation plants.

"Our findings confirm that poor air quality may be a risk factor for bone loss, independent of socioeconomic or demographic factors. For the first time, we have evidence that nitrogen oxides, in particular, are a major contributor to bone damage and that the lumbar spine is one of the most susceptible sites of this damage," said Diddier Prada, Associate research scientist in the Department of Environmental Health Sciences at Columbia Mailman School of Public Health.

Previous studies on individual pollutants have suggested adverse effects on bone mineral density, osteoporosis risk, and fractures in older individuals.

The new study, appearing in the journal eClinicalMedicine, is the first to explore the connection between air pollution and bone mineral density specifically in postmenopausal women, and the first to explore the effects of air pollution mixtures on bone outcomes.

The researchers analysed data of 161,808 postmenopausal women. They estimated air pollution (PM10, NO, NO2, and SO2) exposures and measured bone mineral density (BMD; whole-body, total hip, femoral neck, and lumbar spine) at enrollment and at follow-up at year one, year three, and year six.

The magnitude of the effects of nitrogen oxides on lumbar spine BMD would amount to 1.22 per cent annual reductions -- nearly double the annual effects of age on any of the anatomical sites evaluated. These effects are believed to happen through bone cell death by way of oxidative damage and other mechanisms.

"Improvements in air pollution exposure, particularly nitrogen oxides, will reduce bone damage in postmenopausal women, prevent bone fractures, and reduce the health cost burden associated with osteoporosis among postmenopausal women. Further efforts should focus on detecting those at higher risk of air pollution-related bone damage," said lead author Andrea Baccarelli, from the varsity.