By Wade Rawlins
Much remains to be learned about environmental exposure to asbestos and the incidence of mesothelioma among people who have only "second hand" exposure such as families of asbestos workers or people who live near asbestos plants. That is a focus of new research in Libby, Montana where vermiculite ore tainted with asbestos has caused a high rate of asbestos-related disease. It's also the subject of recently completed research from Egypt.
A study published by researchers in Egypt earlier this year examined environmental exposure to asbestos near Cairo, Egypt and the link to malignant pleural mesothelioma, a rare cancer of the lining of the lungs. The study appeared in the Eastern Mediterranean Health Journal, a publication of the World Health Organization.
The prevalence of mesothelioma, an incurable cancer, has been increasing throughout the industrialized world with the incidence predicted to peak around 2020, the study said. A number of studies have linked exposure to airborne asbestos fibers in the workplace to increased incidence of mesothelioma among workers employed in mining, textile manufacturing, insulation and asbestos cement factories. Families of asbestos workers and those living near asbestos mines and mills also are at increased risk of mesothelioma from environmental exposure, studies suggest.
The Egyptian researchers focused their study on Shubra El-Kheima, an industrial city at the northern edge of Cairo. For decades starting in 1948, the city had a large manufacturing plant that used chrysotile asbestos to make asbestos cement pipe and reinforced concrete products. In 2004, the Egyptian government decided to ban imports of asbestos and the plant closed.
While the plant was still operating full scale, the researchers obtained air samples inside the plant and in neighborhoods up to about 2 miles away. That allowed the researchers to calculate more precisely the amount of asbestos fibers that workers and residents were inhaling and then to estimate the relationship between levels of exposure and rates of mesothelioma.
Researchers did health screenings including x-rays on 487 workers in the plant and on 2,913 residents living in six communities in the vicinity of the plant. They found that about 3 percent of people exposed to asbestos living near the plant had malignant mesothelioma while about 1 percent of the workers did. Both rates exceed the norm. (Because mesothelioma takes 30 to 40 years to appear, it’s not surprising that the number of workers at the plant with the disease was not larger.)
Researchers said a significant finding of the study was that people exposed to asbestos in the environment were at 26 times greater risk of developing mesothelioma than people in a more distant neighborhood, who had no known environmental asbestos exposure nearby.
The community of El-Wehda El-Arabia, directly downwind of the plant, had the highest concentration of asbestos fibers in air samples and also had the highest incidence of mesothelioma among residents of the six communities studied, the researchers found. Thirty-nine residents had malignant pleural mesothelioma.
Researchers also found a correlation between length of exposure to asbestos and rates of mesothelioma. The more years residents were exposed to asbestos, the greater the likelihood of having the disease with a significant increase for those with 40 years or more of exposure. More than 60 percent of the residents with mesothelioma were women, the researchers. They attributed that to their long residence in the area.
The researchers said the study had an important message: the mesothelioma threat will remain for years to come and doctors should look for early signs of mesothelioma in people who had had environmental exposure to mesothelioma.