Occupational and nonoccupational causes of bladder cancer.

An estimated 57,400 new cases of bladder cancer were diagnosed in the US in 2003, and an estimated 12,500 people died as a result of the disease. (1) Cancer of the urinary bladder, as well as in the lower urinary tract lined with transitional cells, can be caused by toxicants contained in cigarette smoke, as well as by a number of occupational exposures. In former decades, bladder cancer was only associated with severe exposure to carcinogenic aromatic amines such as benzidine or [beta]-naphthylamine. But due to the high carcinogenic potential of aromatic amines like benzidine, which has been associated with a 35- to 90-fold increase in bladder cancer risk, it is not surprising that professionals exposed to much lower levels are at elevated risk as well.

In this issue of the Journal Olfert et al review the causes of bladder cancer. (2) Regarding the considerable number of risk exposure, it is of the utmost importance to ask each patient who presents with cancer of the urinary bladder if they have ever had occupational exposure to aromatic amines. Although the production of the most notorious bladder carcinogen, benzidine, has been banned in many countries throughout the 1970s and 1980s, it is worth noting that in South Korea, benzidine production increased in the 1990s, even after it had been banned in Japan. Benzidine production was finally banned in South Korea in 2000. (3) In the US, large-scale production was discontinued in 1976, and only relatively small quantities remain available for diagnostic purposes. In 1972, the estimated benzidine production in the US was 10 million pounds. (4) In connection with this, it is important to know that the latency period of aromatic amine-related bladder cancer is very long, often more than 20 years. Thus the issue continues to be topical.

On the other hand, bladder cancer can also be caused by nonoccupational exposure, especially smoking. It is disappointing that many cases of bladder cancer are due to smoking and thus, in principle, are avoidable. On the other hand, a large pooled study revealed that smoking cessation led to a decreased risk of bladder cancer within just a few years, (5) which is much earlier than had been previously reported.

The strength of the review by Olfert et al (2) is to increase awareness of occupationally caused bladder cancer and to highlight the fact that some exposures might, at some future time, be revealed to be carcinogenic to the bladder.

This is very important, as there has been a remarkable discrepancy between the number of bladder cancer cases in industrialized countries, as estimated by renowned experts, and the number of bladder cancer cases suspected or identified as occupational. In general, it is easy to identify an occupational bladder cancer, if the physician is familiar with the occupations and/or exposures at risk. A challenge remains to identify elevated bladder cancer risks connected with unusual exposures.

References

1. National Center for Chronic Disease Prevention and Health Promotion. Available at: http://www.cdc.gov/TOBACCO/sgr/sgr_2004/Factsheets/2.htm.

2. Olfert SM, Felknor SA, Delclos GL. An updated review of the literature: risk factors for bladder cancer with focus on occupational exposure. South Med J 2006;99:1256-1263.

3. Park J, Kim Y. Dye-manufacturing workers and bladder cancer in South Korea. In: Book of abstracts for the 28th International Congress on Occupational Health June 11-16 2006; Milan, Italy, p 238.

4. US Department of Health and Human Services, Public Health Service National Toxicology Program (2005) Benzidine and dyes metabolized to benzidine. In: Report on Carcinogens, 11th ed. http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s020benz.pdf.

5. Brennan P, Bogillot O, Cordier S, et al. Cigarette smoking and bladder cancer in men: a pooled analysis of 11 case-control studies. Int J Cancer 2000;86:289-294.

Klaus Golka, MD

From the Institute for Occupational Physiology at the University of Dortmund, Leibniz Research Centre for Working Environment and Human Factors, Dortmund, Germany.

Reprint requests to Dr. Klaus Golka, Institute for Occupational Physiology at the University of Dortmund, Ardeystr. 67,44139 Dortmund, Germany. Email: [e-mail]

Accepted August 10, 2006.