University of Michigan School of Public Health Study
In March 2007, Dr. Hal Morgenstern released a cancer incidence study of the communities surrounding SSFL:
- Cancer Incidence in the Community Surrounding the Rocketdyne Facility in Southern California, March 2007
This study had been commissioned by the Agency for Toxic Substances Disease Registry. The study concluded that:
- Associations between distance from SSFL and cancer incidence differed by
type of cancer outcome. Standardized incidence rate ratios were close to 1, indicating little or no
association, for total cancers and radiosensitive cancers among adults; but the incidence rate of
chemosensitive cancers was slightly elevated during both follow-up periods in the population
living within 2 miles of SSFL. Results for the 9 specific cancers revealed some elevated
incidence rates between 1988 and 1995 among persons living within 2 miles of SSFL.
Specifically, the standardized incidence rate ratio was greater than 1.6 for cancers of blood and
lymph tissue, bladder, thyroid, and upper aerodigestive tract. Between 1996 and 2002, the rate
ratio among persons living within 2 miles of SSFL was greater than 1.6 for thyroid cancer.
There were too few childhood cancers to yield informative results.
- The strongest and most consistent association observed in this study was for
thyroid cancer, which was associated with distance from SSFL in both follow-up periods. This
finding may have public-health significance because perchlorate, a component of rocket fuel
used in large quantities at SSFL, is known to disrupt thyroid function, it has been shown to
induce thyroid tumors in laboratory animals, and there is evidence from two other investigations
that perchlorate migrated offside to contaminate the groundwater in areas surrounding SSFL. In
addition, findings from one of those other studies suggest that the 1959 partial meltdown of a
nuclear reactor at SSFL could have released appreciable amounts of radioactive cesium and
iodine, which might have increased the incidence of thyroid cancer in the population surrounding
SSFL. Furthermore, our results for cancers of the bladder, blood and lymph tissue, and upper
aerodigestive tract are consistent with associations observed in the UCLA Worker Study between
mortality from these cancers and occupational exposures to radiation and chemicals.
It is important to recognize that associations observed between distance from SSFL and
the incidence of specific cancers are based on small numbers of cases in the region closest to
SSFL. Thus, these associations are estimated imprecisely and may represent chance findings. In addition, observed associations may have been biased by certain methodologic limitations—use
of distance from SSFL as a crude proxy measure for environmental exposures, mobility of the
residential population before and during the follow-up period, and lack of information on other
cancer risk factors, such as cigarette smoking and socioeconomic status, that might distort the observed associations.
- Despite the methodologic limitations of this study, the findings suggest there may be elevated incidence rates of certain cancers near SSFL that have been linked in previous studies with hazardous substances used at Rocketdyne, some of which have been observed or projected to exist offsite. There is no direct evidence from this investigation, however, that these observed associations reflect the effects of environmental exposures originating at SSFL. Given these provocative findings and unanswered questions, it is tempting to recommend further analyses or future studies to address the health concerns of the community. Unfortunately, it is not clear at this time whether such additional analyses or studies will be sufficient to determine whether operations and activities at Rocketdyne affected, or will affect, the risk of cancer in the surrounding neighborhoods.