cystitis in showing decreased urinary glycosaminoglycan excretion.

Advances in understanding and using biologic markers should assist in identifying xenobiotics that are toxic to the urinary tract. The functional role of the urinary tract, including clearance of toxic substances from the blood, predisposes it to xenobiotic exposure and toxicity. Historically, identification of the type and amount of xenobiotic exposure has been difficult, often because of the interval between exposure and the onset of disease. Blacks and other minority groups, for reasons that are not entirely apparent, are at higher risk.

In diseases such as bladder cancer, xenobiotics associated with particular occupations are strongly implicated, and their mutagenic effects may be important. However, in kidney cancer and other renal diseases, a number of host factors, the typically low levels of exposure to multiple xenobiotics, and such confounding variables as smoking and genetic susceptibility often mask the epidemiologic significance of individual xenobiotics. A powerful approach toward unraveling the complexities of xenobiotic exposure is to integrate biologic markers of susceptibility with biologic markers of effect.

Some xenobiotics are known to cause acute renal failure. Heavy metals and organic solvents stand out in this regard. There are several well-established associations between xenobiotic exposure and the development of chronic renal failure, as exemplified by exposures to lead and cadmium. The association of bladder cancer and occupational exposure to aniline dyes serves as a paradigm for the potential adverse health effects of xenobiotics.

Environmental agents have also been implicated in the development of neoplasms in the kidney. Some of these can be facilitated by acquired or inherited genetic defects. The association of xenobiotic exposure and such conditions as prostate cancer and interstitial cystitis is less certain but merits attention.