More Questions Than Answers About Health Near Rocky Flats

For decades, the Colorado Department of Public Health and Environment has cited its cancer-registry studies as evidence that it has not found elevated cancer rates among residents living near Rocky Flats. But what did those studies actually examine—and what important questions remain unanswered?

The lack of clear, prominent communication about the studies’ limitations—combined with study areas extending well beyond documented contamination zones, boundaries based largely on geographic proximity rather than individual exposure, and the use of the remainder of metropolitan Denver as the comparison population—raises more questions than it answers about the health of communities affected by Rocky Flats.

What the studies established

CDPHE compared cancer incidence within ten large geographic areas surrounding Rocky Flats with the incidence expected from cancer rates in the remainder of metropolitan Denver.

For many of the cancer categories examined, the studies did not find statistically higher incidence in the ten study areas when compared with the selected Denver metro population.

That is a legitimate but narrow statistical finding. It does not answer the broader question residents have been asking:

Did exposure to contaminants released from Rocky Flats increase cancer risk or otherwise harm the health of people who lived nearby?

The studies were not designed to answer that question.

The study areas were not exposure-defined populations

The ten Regional Statistical Areas used by CDPHE were selected primarily because of their geographic proximity to Rocky Flats. They were not created by identifying people who were exposed or by following the documented movement of Rocky Flats contaminants. These were large geographic areas containing people with potentially very different exposure histories. Some may have lived in contaminated areas for decades. Others may have lived outside the primary contamination pathways or moved into the area long after the major historical releases.

Combining these residents within large geographic units can dilute a health pattern concentrated within a smaller, more highly exposed population. CDPHE acknowledges this possibility in the detailed limitations of its reports, including the possibility that exposure misclassification could make a health effect more difficult to detect. That warning should be understood alongside every conclusion that cancer incidence was “not higher than expected.”

The comparison population raises another question

CDPHE calculated the expected number of cancers using cancer rates from the remainder of metropolitan Denver. The reports state that people outside the ten study areas were assumed to be beyond—or within the lower range of—possible Rocky Flats health effects. But portions of metropolitan Denver have appeared within historical maps documenting the movement and deposition of Rocky Flats-related contamination. This does not prove that Denver residents received harmful exposures. It does raise a significant methodological question: Was the remainder of metropolitan Denver an appropriate comparison population?

If part of the comparison population experienced some degree of the same environmental exposure, the difference between the study and comparison groups could be reduced. That could make an elevation more difficult to detect.

The studies did not follow the people who were there

CDPHE’s analyses did not reconstruct the population that lived near Rocky Flats during the years of plant operations, major fires, documented releases, and other potential exposure events.

The studies did not:

• Determine which individuals were exposed.

• Measure individual exposure or radiation dose.

• Reconstruct complete residential histories.

• Determine how long each person lived near Rocky Flats.

• Follow former residents after they moved away.

• Adequately account for migration into and out of the study areas.

• Connect the timing of residence and exposure with the latency of individual cancers.

• Follow a defined group of potentially exposed residents over time.

  
  

Instead, the analyses generally classified cancer cases according to where people lived when they were diagnosed. A person who lived near Rocky Flats during a relevant exposure period but moved away before developing cancer would not necessarily be counted as part of the Rocky Flats study population. Conversely, someone who moved into the area shortly before diagnosis could be counted even if that person had little or no relevant historical exposure.

Cancer-registry surveillance is not longitudinal health monitoring

CDPHE maintains an important statewide cancer registry and has periodically analyzed cancer incidence in geographic areas around Rocky Flats. That is cancer-registry surveillance.

It is not the same as longitudinal health monitoring of an exposed community. A longitudinal cohort study would identify people who lived within relevant exposure areas during defined historical periods and follow their health outcomes over time—including after they moved. It would attempt to reconstruct residential histories, distinguish different exposure zones, consider latency, and compare the cohort with an appropriately selected reference population.

No such longitudinal cohort study of Rocky Flats-area residents has been conducted.

Other research designs—including case-control studies, exposure reconstruction, residential-history analyses, and biomonitoring—could also contribute important evidence. But repeated ecological comparisons using residence at diagnosis cannot substitute for studying the people who were actually present during the relevant exposure periods or during residual exposure periods.

What can we responsibly conclude?

The most scientifically responsible conclusion is:

CDPHE’s existing ecological cancer-registry studies cannot provide a definitive answer about the health effects of Rocky Flats exposure on affected residents.

The limitations are not minor technical details. They determine what the studies can detect, what they may miss, and what conclusions the public can reasonably draw. Until an independent, multidisciplinary review examines the study boundaries, comparison population, exposure assumptions, migration, latency, statistical methods, and public communication—and until stronger health research is conducted—the actual health experience of people affected by Rocky Flats remains an open question.

That is why these studies raise more questions than answers—and why the communities surrounding Rocky Flats still deserve better research.