Colorado’s top medical official has criticized a team of researchers for misusing state health records to suggest a link between energy development and childhood cancer.

“[T]his study’s conclusions are misleading in that the study questions a possible association between oil and gas operations and childhood leukemia; it does not prove or establish such a connection,” Dr. Larry Wolk, chief medical officer and executive director of the Colorado Department of Public Health and Environment (CDPHE), said in response to a request for comment from Western Wire.

Dr. Larry Wolk (photo credit: Flickr / CSU)

Wolk said actual emissions monitoring from across the state shows that living near oil and gas development is no different to living in Denver.

“CDPHE’s analysis of air quality data in high oil and gas areas of Colorado spanning the last six years and encompassing more than 10,000 individual samples indicate benzene exposures are within EPA’s generally acceptable cancer risk range and are similar to those of Denver,” Wolk, a practicing physician and an award-winning pediatrician, said in a statement.

The research paper itself includes a concession that “[t]he CDPHE disclaims responsibility for any analyses, interpretations, or conclusions” made by the authors, who used the health department’s data to conduct their analysis. It is the second time CDPHE officials have criticized the lead researchers responsible for today’s paper and publicly challenged their findings.

In his statement, Wolk says the paper’s “lack of a conclusive association” is the “result of many limitations.” Those limitations include that the research paper “relies on administrative data” instead of actual environmental exposures, he said. The paper “compared leukemia cases to other cancer cases, rather than comparison to healthy people which makes findings more difficult to interpret,” and its conclusions are “driven by only 16 cases which significantly limits the strength of the finding,” Wolk said.

The paper failed to “adequately address additional or alternate explanations for findings, specifically differences in population demographics, smoking history and exposure to other environmental factors,” Wolk said. The researchers also didn’t have full address histories for patients whose records they reviewed. That’s important because earlier research has shown up to two-thirds of people move during the time period of a study of this kind, he said.

The dispute between Wolk and the researchers, led by assistant research professor Lisa McKenzie at the Colorado School of Public Health (CSPH), goes back years. In 2014, Wolk issued a similar statement to debunk the findings of another paper that tried to blame birth defects in Colorado on oil and natural gas development.

Years before that, a team of CSPH researchers clashed with public health officials in Garfield County, Colo. Initially hired to conduct a health impact assessment for planned oil and gas development in the area, the researchers were fired in 2011, according to the Denver Business Journal. But in 2012, without the county’s knowledge, McKenzie and her fellow researchers used the data they collected to claim residents living within half a mile of the proposed new wells faced higher health risks.

The half-mile assertion has been a central talking point of anti-oil and gas groups ever since. McKenzie’s work was used by Food & Water Watch, for example, to justify calls for a statewide ban on oil and gas development in Colorado. Later, a coalition of “keep it in the ground” groups – including Food & Water Watch, and the Sierra Club – used the half-mile claim in support of a proposed ballot measure that would ban drilling within 2,500 feet of areas of “special concern,” including buildings and open space.

If the 2,500-foot setback were imposed, it would effectively ban drilling across 90 percent of the state, according to an analysis performed by the Colorado Oil & Gas Conservation Commission last year. But the measure was never put to voters because anti-oil and gas groups could not gather enough signatures to place the initiative on the ballot.

At the same time, Wolk and McKenzie have engaged in a back-and-forth through the press. In Weld County, where nearly half of Colorado’s oil and gas wells have been drilled, public health officials see “no reason to believe that there is a causal relationship between oil and gas operations and chronic diseases or cancers,” Wolk told the Greeley Tribune last August. He also warned that the public shouldn’t be “misled” into believing otherwise.

In response, McKenzie has admitted her research does not show a causal link between oil and gas development and health impacts. But publishing papers that suggest there could be a connection is a good way to secure bigger research grants, she said. You publish “the less expensive, simpler studies first, and if those are indicating there might be potential for health defects, that provides justification for the larger studies,” McKenzie told the Tribune.

In a statement today, the researchers listed some of the paper’s shortcomings and called for “[m]ore comprehensive research that can address our study’s limitations.”

“The study was limited by the low occurrence of leukemia and non-Hodgkin lymphoma in rural Colorado, lack of specific age at cancer diagnosis and the fact that all study participants had been diagnosed with cancer,” according to the statement. “The study also was limited by the lack of information on specific activities at the well sites, place of residence before cancer diagnosis, other sources of pollution around the residence and individual characteristics such as common infections and family history of cancer.”

According to the Broomfield Enterprise, McKenzie has been invited to testify as a public health expert at an upcoming city hearing on oil and gas development. In 2013, Food & Water Watch led a local campaign to halt oil and gas development in Broomfield, but the Colorado Supreme Court subsequently ruled such bans are unlawful. The Broomfield City Council is now debating a new six-month oil and gas development ban, according to the Denver Business Journal.