Following the the collapse of the World Trade Centre in 2001 firefighters and other emergency crew workers inhaled vast amounts of 'dust'.
As a result, according to a team of researchers in New York, that exposure has created lung problems which equate to 12 years of age-related respiratory decline.
Dr. Gisela I. Banauch and colleagues at Montefiore Medical Center in New York were able to compare the lung tests of 12,079 rescue workers in the year after the disaster to lung function tests carried out before the attacks.
Banauch and her team had access to respiratory function results of New York City Fire Department workers from 1997 onwards because routine lung tests were carried out every 18 months as part of routine medical screening.
Their investigation showed that those present when the North and South Towers collapsed or arrived later that morning, suffered the most damage and some still had breathing problems.
The researchers say there was a substantial reduction in forced expiratory volume, the amount that can be breathed out in one second, in the year after September 11 2001.
It seems 13.7% of the rescue workers were exposed to the most amount of dust by arriving on the morning of the disaster and being present when the towers collapsed, while a further 67.8% arrived on the scene two days after the collapse, and 16% arrived after the third day.
The most severe and frequent respiratory symptoms were experienced by those exposed in the first days after the collapse and were worse than workers who arrived later.
Although only 22% of workers who arrived early reported wearing a mask on the first day, that had increased to 50% by the third day, but the researchers say it did not appear to have had a protective effect.
Dr. Banauch who is an associate professor of medicine at Albert Einstein College in New York says some of the effects were the result of acute irritation of the airways but that smaller follow-up studies showed some rescue workers were suffering from more long-term effects.
She says many rescue workers developed such symptoms as cough, wheezing and shortness of breath, but the two most common respiratory diagnoses have been reactive airways dysfunction syndrome (RADS) and irritant-induced asthma and for a significant number of workers, this has affected their ability to work.
Banauch says she believes that when the towers collapsed building materials were pulverised and there was a lot of cement in the dust, which is very alkaline and causes burns.
She says ideally adequate respiratory protection should be available promptly for first responders, but that is not easy to implement.
Dr. John R. Balmes, of the University of California at San Francisco, in an accompanying editorial says better preparation for future disasters is needed including plans to protect emergency responders from unnecessary occupational exposures to irritant dusts.
The study was co-authored by Dr. David Prezant, the Fire Department's deputy chief medical officer, and is published in the current issue of the American Journal of Respiratory and Critical Care Medicine.