Women over 50 are already at a higher risk of osteoporosis, but a new study from Columbia University’s Mailman School of Public Health in New York has determined that elevated levels of air pollutants can contribute to bone damage in postmenopausal women.

The study found that the effects of air pollution were most evident in the lumbar spine, “with nitrous oxides twice as damaging to the area than seen with normal aging,” according to a press release about the study.

Vehicle exhaust is a major source of nitrous oxides, in addition to 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,” said Dr. Diddier Prada, study first author and associate research scientist in the Department of Environmental Health Sciences at Columbia Mailman School of Public Health, said in a press release. “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.” 

Osteoporosis is a bone disease that occurs when bone mineral density and bone mass decrease, which can lead to a decrease in bone strength and an increase in fractures, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Approximately 2.1 million osteoporosis-related bone fractures occur annually and the disease impacts women more than men as 80% of the estimated 10 million Americans with osteoporosis are women. Each year, osteoporotic fractures result in up to $20.3 billion in direct health costs.

Postmenopausal women are at a higher risk, as one in two women over the age of 50 are likely to experience a bone fracture as a result of osteoporosis. In addition to reducing bone mineral density and increasing the risk for bone fracture later in life, air pollution is also associated with cardiovascular and respiratory diseases, lung cancer, and impaired cognition. 

Researchers analyzed data from the long-standing Women’s Health Initiative, an ethnically diverse study of 161,808 postmenopausal women. Participants were between the ages of 50 and 79 years during enrollment from September 1994 through December 1998. Data was analyzed from January 2020 to August 2022. 

At the time of enrollment, a little more than 9,000 women had bone mineral density and long-term air pollution data available. Researchers measured whole-body, total hip, femoral neck, and lumbar spine bone mineral density at enrollment and followed up during year one, year three, and year six using dual-energy X-ray absorptiometry, also known as a DEXA scan.  

Researchers found that lumbar spine bone mineral density amounted to 1.22% annual reductions, which is nearly double the annual effects of age on any of the anatomical sites evaluated. They also noted 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,” lead author Dr. Andrea Baccarelli, chair of the Department of Environmental Health Sciences at Columbia Mailman School of Public Health, said in a press release. “Further efforts should focus on detecting those at higher risk of air pollution-related bone damage.”