Exposure to poor environmental quality increases cancer incidence

County-level cancer incidence rates appeared higher in areas with poor environmental quality, according to study results published in Cancer.

“Our study is the first we are aware of to address the impact of cumulative environmental exposures on cancer incidence,” Jyotsna S. Jagai, MS, MPH, PhD, environmental health scientist in the division of environmental and occupational health sciences at University of Illinois at Chicago, said in a press release. “This work helps support the idea that all of the exposures we experience affect our health and underscores the potential for social and environmental improvements to positively impact health outcomes.”

Earlier studies have suggested that environmental factors — which include domains in air, water, land quality, sociodemographic environment and built environment — can interfere with biological processes and affect risk for cancer.

However, research to date has focused on individual environmental exposures and cancer. Cancer development is dependent on all exposures individuals may face, all of which need to be taken into consideration, according to Jagai.

“We must consider the overall environment that one is exposed to in order to understand the potential risk for cancer development,” Jagai said.

Jagai and colleagues combined national county-level cancer incidence data from the NCI state cancer profiles with data from the Environmental Quality Index (EQI), a measure of cumulative ambient environmental exposures in the United States between 2000 and 2005.

The researchers sought to determine any associations between cancer incidence and the EQI and domain-specific indices based on rural and urban status. They focused on the leading three causes of cancer among men (lung, prostate and colorectal) and women (lung, breast and colorectal).

The analysis included 2,687 counties (34% metropolitan urbanized; 10% nonmetropolitan urbanized; 35% less urbanized; 21% thinly populated).

Researchers found a positive association between all-site county-level cancer incidence and poor environmental quality overall (incidence rate difference [IRD] = 38.55; 95% CI, 29.57-47.53), as well as among men (IRD = 32.6; 95% CI, 16.28-48.91) and women (IRD = 30.34; 95% CI, 20.47-40.21).

Further, researchers linked all-site county level cancer incidence to poor air quality (IRD = 44.19; 95% CI, 34.84-53.54). This association persisted across rural and urban areas, indicating all-site cancer incidence increased as air quality worsened, the researchers noted.

Researchers used county-level models to measure environmental drivers of incidence rates for the top three cancer sites.

Prostate cancer appeared positively associated with poor environment in the air domain (IRD = 10.09; 95% CI, 1.84-18.34), built domain (IRD = 8.98; 95% CI, 8.98; 95% CI, 2.54-15.41) and sociodemographic domain (IRD = 10.39; 95% CI, 3.38-17.41).

Breast cancer appeared positively associated with poor air quality (IRD = 3.69; 95% CI, –0.35 to 7.73), poor built environment (IRD = 5.59; 95% CI, 2.04-9.14) and poor sociodemographic environment (IRD = 5.01; 95% CI, 0.82-9.2).

In general, these associations persisted across the rural–urban domains, with the exception of thinly populated areas.

Researchers linked lung cancer with poor air quality in the non-metropolitan urbanized (IRD = 12.78; 95% CI, 3.95-12.61) and less urbanized (IRD = 8.5; 95% CI, 2.12-14.88) areas in men, and the metropolitan urbanized stratum in women (IRD = 5.01; 95% CI, 1.31-8.71).

These data are an example of how environmental geospatial data are “essential” to cancer control and public health, Scarlett Lin Gomez, PhD, MPH, research scientist from the Cancer Prevention Institute of California, and colleagues wrote in a related editorial.

“These data are fundamental to documenting which communities are most valuable in terms of high cancer rates, and which geographically determined factors may be driving community-level disparities,” Gomez and colleagues wrote.

However, the Local Zoning Decisions Protection Act of 2017 and other efforts to suppress the collection and use of these data for research could pose a problem for future, valuable research, they added.

“H.R.861, which was introduced on February 3, 2017, to ‘terminate the Environmental Protection agency’ — the source of the environmental data used in the study by Jagai [and colleagues] — will have severe repercussions on the scientific community’s ability to produce this type of valuable research,” the researchers wrote. – by Melinda Stevens

Disclosure: The researchers report no relevant financial disclosures. Gomez and colleagues report no relevant financial disclosures.