Higher Rate of Bladder Cancer Found East of Lab : Rockwell: A state report cites 37 cases found in one of three census tracts in Canoga Park and Chatsworth.

Elevated rates of bladder cancer have been found in three census tracts east of Rockwell International’s Santa Susana Field Laboratory, according to a preliminary state health report that drew no conclusions about the cause of the increase.

The six-page report, dated October but released only Monday, said bladder cancer rates were about 50% higher in the three census tracts in Canoga Park and Chatsworth than for Los Angeles County as a whole. In two of the census tracts, the finding was not statistically significant, the report said, meaning that it could be due to a statistical variation common in such studies rather than to an actual increase in bladder cancer.

In the third, the increase from 1983 through 1987 was a statistically significant jump to 37 cases, about half again as many as researchers would expect to find in such a group.

The report said cancer data for Ventura County census tracts near the plant will not be available until later this year. The lab is southeast of Simi Valley in the 23900 block of Woolsey Canyon Road.

Robert L. Holtzer, a public health medical officer with the state Department of Health Services, said residents should not be alarmed by the data. “Right now, we’ve got something that we don’t have an explanation for,” he said. It “could be mathematical. It could be real disease,” he said, adding that bladder cancer in the study area is still quite rare.

The data was compiled by the cancer surveillance section of the Department of Health Services as part of a preliminary study of the health of residents within a five-mile radius of the Santa Susana lab.

The laboratory was the target of protests by neighbors and environmentalists, concerned about reports of pollution there, from 1989 until last year, leading company executives to eliminate nuclear work at the site.

Since the 1950s, the 2,668-acre Santa Susana site has been used for rocket testing, and was formerly a major center for nuclear development and research under Rockwell contracts with the U. S. Department of Energy. State health officials have asked the DOE for $341,361 for a study to determine if past chemical or radioactive releases could have affected the health of nearby residents.

This study proposal and the preliminary cancer data are to be discussed this morning in Simi Valley at a meeting of a federal, state and local interagency work group monitoring environmental cleanup at the Rockwell site.

According to a state health memo, “various activities” at the Santa Susana laboratory “may have created significant environmental releases of hazardous materials over the lengthy operation period of the site.” But the memo stressed that the bladder cancer findings “are preliminary and not necessarily related” to the lab.

It did not speculate on how people miles from the plant could have been exposed to significant contamination.

“I don’t believe there’s anything coming from Santa Susana that would be even remotely related to bladder cancer,” said Dr. Arlene Giliberto, an epidemiologist employed by Rockwell’s Rocketdyne Division, which operates the Santa Susana site.

The preliminary report considered rates for various types of cancer in five census tracts in Woodland Hills, Canoga Park and Chatsworth that are within five miles of Santa Susana. For each of the census tracts, the rates were computed for 1978-82 and 1983-87, and compared to countywide rates.

In some of the tracts, rates for certain cancers were somewhat higher or lower than average, but the report called this consistent with random variation in cancer rates.

However, bladder cancer rates were elevated in the three tracts nearest to Santa Susana--bordered roughly by the Simi Valley Freeway on the north, Vanowen Street on the south, Canoga Avenue on the east and the Los Angeles-Ventura county line on the west. Bladder cancer strikes about 16 of every 100,000 people per year; in those tracts, the rate was about 24.

The statistically significant incidence was found in the northernmost tract, north of Roscoe Boulevard.

Bladder cancer has been associated with worker exposure to aniline dyes and with cigarette smoking. The report said smoking probably does not explain the bladder cancer data because rates for lung cancer--which is more strongly linked to smoking--were about average in the tracts.

The report said some of the increase is probably attributable to ethnicity, since whites are more likely to contract bladder cancer than Latinos, and the ratio of whites to Latinos in the three tracts is higher than for the county as a whole. However, the study said, if it were merely a question of the proportion of whites, bladder cancer rates in the two neighboring tracts should also have been higher.

Dr. Charles Haskell, an oncologist and professor of medicine at UCLA, said the report does not show “a dramatic increase.” But he said the data “can have important public health implications” and ought to be pursued.

Holtzer said the grant that the state has requested from the federal government would fund a year of study on potential past exposures of neighbors of the Santa Susana complex.

John Belluardo, a spokesman for the DOE in Oakland, said “there is general support for” making the grant. He said “it’s under serious consideration” but “has not been finalized yet.”