PAINTERS HAVE INCREASED BLADDER CANCER RISK

July 22, 2010 — Painters and others exposed to paint on the job are at significantly greater risk of developing bladder cancer than other workers, even when potential confounders, such as smoking and other occupational exposures, are taken into account, say authors of a meta-analysis of 41 studies.

Neela Guha, PhD, MPH, and colleagues from the International Agency for Research on Cancer in Lyon, France, report their findings in the August issue of Occupational and Environmental Medicine.

The overall summary relative risk (RR) for bladder cancer in painters was 1.25 (95% confidence interval [CI], 1.16 - 1.34); the risks did not diminish after adjustment for smoking status (RR, 1.28; 95% CI, 1.15 - 1.43) or other occupational exposures (RR, 1.27; 95% CI. 0.99 - 1.63).

The risks were significantly higher for women (RR, 1.55; 95% CI, 1.08 - 2.23) than for men (RR, 1.24; 95% CI, 1.15 - 1.34); this difference was statistically significant, even though the data on women painters came from only 4 studies, the investigators note.

In addition, the RR for veteran painters — those with more than 10 years of exposure — was 1.81 (95% CI, 1.20 - 2.75), compared with those who had less than 10 years of exposure (RR, 1.41; 95% CI, 1.00 - 2.01).

Population at Risk

The population at risk might include people who apply paint to surfaces for a living and to allied trades, such as plasterers, wallpaper hangers, and wood refinishers (French polishers), the researchers note. The findings are largely on based data from 30 case–control studies, but include 2 cohort studies and 8 record-linkage studies spanning 50 years.

"Because several million people are employed as painters worldwide, even a modest increase in the relative risk is remarkable. It is important for cancer control and prevention to design studies with more specific exposure assessment that quantifies individual agents or classes of agents to identify the underlying carcinogenic agents encountered in painting," the investigators note.

They point out that the association between bladder cancer and painting remained even when smoking was taken into consideration. Cigarette smoking is responsible for about two thirds of bladder cancer cases in men and about one third of cases in women the industrialized world, they note, adding that the excess risk is likely attributed to aromatic amines in smoke, some of which are found in paint.

Real Risk Is Low

These results are interesting but not surprising, and the strength of the association is fairly mild, said J. Stephen Jones, MD, professor of surgery and chair of the Department of Regional Urology at the Cleveland Clinic in Ohio, in an interview with Medscape Medical News.

Dr. Jones noted that the RR of about 1.25 and the CIs ranging from 1.16 to 1.34 are similar to previous reports in the literature. However, the real risks are actually still fairly low, he said.

"Let's say that people have a 1 in 100 chance of getting bladder cancer in their lifetime. That's a very small increase for any given person that they actually might get bladder cancer. So although the numbers start sounding kind of concerning, when you really think about [how much] Mr. Smith going to work in the morning [increases] the risk that he, in his lifetime, is going to get bladder cancer, he's still not going to get bladder cancer the overwhelming majority of times. That why most painters don't get bladder cancer," he said.

Arnold Chin, MD, PhD, a urologist at the Ronald Reagan UCLA Medical Center in Los Angeles, California, and researcher at UCLA's Jonsson Comprehensive Cancer Center, told Medscape Medical News that a different recently published meta-analysis looking at risks for bladder and lung cancer in painters found no increased risk for either cancer, compared with nonpainters (Crit Rev Toxicol. 2010;40:101-125).

The authors of that meta-analysis write: "Residual confounding by smoking and socioeconomic status, lack of exposure group effect, and publication bias limit the ability of the meta-analyses to explain associations observed between occupational painting and lung and bladder cancers. Given the long latencies for lung and bladder cancers, these weak associations, if real, may not be elucidated through studies of occupational painting today."

Neither Dr. Jones nor Dr. Chin were involved in either study, and were approached for independent comment by Medscape Medical News.

The authors, Dr. Jones, and Dr. Chin have disclosed no relevant financial relationships.

Occup Environ Med. 2010;67:568-573. Abstract