PROVIDENCE, R.I. — A study published in the American Journal of Public Health finds links between mining and the spread of tuberculosis in sub-Saharan Africa. The study analyzed data from 44 sub-Saharan African countries and found that the greater the mining production, the higher the country’s incidence of TB. The research concluded that as many as one-third of new TB cases — 750,000 cases annually — may be attributable to mining.
“We have long known that the conditions on the mines — both above and below ground — are conducive to the spread of TB and HIV. But this is the first time we have used statistical techniques to accurately quantify the contribution of mining to TB,” said Mark Lurie, assistant professor of medical science at Brown University. Lurie says that TB incidence in some mines is 10 times times higher than in the general population.
The study, which included researchers from Oxford University, London School of Hygiene and Tropical Medicine, and the University of California — San Francisco, attributes the high incidence of TB among miners to factors including silica dust in mines, crowded working and living conditions, and the rampant spread of HIV, which weakens the body’s immune system. Many of the mineworkers are migrants, meaning that they have exposure to multiple TB risk factors, including health-care disruption and low socioeconomic status. The children, wives and friends of these workers are also at risk, given the migratory pattern that has most miners traveling back and forth from their home countries several times a year.
TB has been on the rise in sub-Saharan Africa for the last 20 years, during which time incidence of TB has doubled from 173 to 351 cases per 100,000 population. Lurie found that TB is on the decline in only 10 of the 44 African countries examined. It was long believed that the rise in TB was a result of the high rate of HIV infection, but Lurie and his colleagues discovered that HIV is only one factor contributing to the high TB rates and that mining is a significant additional factor. The researchers found, for example, that when countries reduced their mining activity, TB rates fell more quickly than in neighboring countries with stable or increasing mining rates.
TB is a contagious disease. Like the common cold, it spreads through the air. Only people who are sick with TB in their lungs are infectious. When infectious people cough, sneeze, talk or spit, they propel TB germs, known as bacilli, into the air. Infection occurs when a susceptible person inhales these bacilli. Rates of TB in the United States have been declining with 4.6 cases per 100,000 population in 2006, approximately one-seventieth of the rates seen in sub-Saharan Africa, according to the World Health Organization.
“It is a sad irony that precious minerals and metals coveted around the world cause such great harm in their production,” said Lurie. “Our research points to the urgent need to improve the living and working conditions on African mines as an effective public health intervention.”