Workers exposed to pesticides and herbicides on the job may be more likely than other people to develop chronic obstructive pulmonary disease (COPD), bronchitis and other breathing problems, an Australian study suggests.

With any herbicide exposure at work, people were more than twice as likely to develop COPD by middle age, and workplace pesticide exposure was associated with 74 per cent higher odds of the common lung disease, researchers report in Thorax.

Over a lifetime, pesticides and herbicides may pose an even bigger added risk for breathing disorders, the study also found.

Each 10-year increase in occupational exposure to pesticides carried a 12 per cent increased risk of COPD and a 16 per cent higher risk of developing chronic bronchitis. Every extra decade of herbicide exposure, meanwhile, carried a 22 per cent increased risk of bronchitis, while each 10 years of insecticide exposure was associated with 15 per cent higher odds of bronchitis.

“Our study looked at long-term exposure to pesticides and it is thought that long-term exposure to pesticides increases mucus secretion and muscle contraction in the lungs, causing breathlessness, cough and wheeze,” lead study author Sheikh Alif of the University of Melbourne in Australia said. Globally, more than 65 million people have moderate to severe COPD and the condition causes about five per cent of all deaths, according to the World Health Organisation.

Most cases are caused by smoking or exposure to second-hand smoke but working or cooking around certain toxic dusts, chemicals and fuels can also contribute, as can frequent respiratory infections during childhood.

For the current study, researchers examined data collected on 1,335 workers from 2002 to 2008, including information on workplace exposure to pollutants as well as results from tests to detect COPD and other respiratory issues.

Study participants were 45 years old on average, 87 per cent were currently employed and 25 per cent were current smokers.

Overall, six per cent of them had COPD, 8.6 per cent had chronic bronchitis, and more than 28 per cent reported having asthma currently or previously.

In addition to risks associated with pesticides and herbicides, the study also found workers who didn’t have asthma had an increased risk of COPD when they had any exposure to toxic mineral dust, gases, fumes and vapors.