It’s common knowledge that individual harmful environmental exposures, such as radon, pesticides, and air pollution, may increase specific cancer risks in a city or region. However, new research reveals that the overall environmental quality of a geographic location is also associated with overall cancer incidence.
Counties in the United States with the poorest environmental quality rating had an average of 38 more cancer cases per 100,000 people than counties with the highest rating over the study period (2000 to 2010), report the authors, led by Jyotsna S. Jagai, PhD, MPH, from the University of Illinois, Chicago.
“Research focusing on single environmental exposures in cancer development may not address the broader environmental context in which cancers develop,” observe the authors.
Their new study, which relied heavily on data from the now-embattled US Environmental Protection Agency (EPA), was published online May 8 in Cancer.
The team also showed that specific cancers may be tied to overall environmental conditions. Prostate and breast cancers demonstrated the strongest positive associations with poor environmental quality, they report.
In the study, the researchers used a novel instrument, the Environmental Quality Index (EQI), which measures US county-level exposures in five domains: air, water, land, built environment, and socioeconomics. The EQI contains data from 2000 to 2005 and is a publicly available data source from the EPA. Two of the study authors are employees of the federal agency.
Each EQI domain used in the study had multiple variables. For example, the water domain included measurements of the quality of recreational water, drinking water, and chemical contaminants. The land domain included measures of pesticides, contaminants, types of facilities, and radon. The built environment included public transportation quality, roads, businesses, and housing.
A map of the EQI shows the scores for each US county.
The researchers linked EQI to county level, age-adjusted annual cancer incidence rates from Surveillance, Epidemiology, and End Results program state cancer profiles. These rates were available for 85% of all counties in the United States. The investigators evaluated the incidence rates for “all-site” (ie, overall) cancer and the top three cancers by sex.
The EQI was determined for each county for the years 2000 to 2005. The team then assessed relationships between the EQI and the cancer incidence rates from 2006 to 2010 in order to allow for some lag time in disease development.
Among other things, the researchers compared the cancer rates in the highest and lowest environmental quality quintiles.
In an accompanying editorial, a group of four experts write that “more than 30 cases of cancer per 100,000 persons per year…could be avoided if environmental quality were improved from the worst to the best quintile.”
However, the new findings do not account for the effect of confounders (such as alcohol use and overweight) and other factors, such as competing causes of death, say the editorialists, led by Scarlett Lin Gomez, PhD, from the Cancer Prevention Institute of California in Fremont.
Study author Dr Jagai told Medscape Medical News that the study design did adjust for county-level percentage of population that ever smoked.
“This is the best we can do for this type of analysis since we are considering county-level incidence and do not have individual-level information,” she said.
The editorialists also highlighted that associations between environmental quality and cancer incidence were most pronounced in more urbanized counties and for the air, sociodemographic, and built environment domains.
What the New Study Contributes
Previous research has shown that cancer health disparities exist geographically, write the editorialists. The new study contributes to the growing understanding of this phenomenon by examining the domains through which these disparities arise, they assert. The hope is that policymakers will target specific regions and environmental factors to reduce an area’s cancer burden, they add.
The editorialists hope that data for this type of analysis, known as geospatial research, continues to be available to researchers.
Dr Gomez and colleagues are concerned about efforts to “suppress the federal collection of geospatial data.” Legislation in the US Congress, including H.R.482 and companion bill S.103, were introduced in January. The bills, entitled Local Zoning Decisions Protection Act of 2017, “aim to nullify fair housing regulations,” they say. The cite the bill, which says, “Notwithstanding any other provision of law, no Federal funds may used to design, build, maintain, utilize, or provide access to a Federal database of geospatial information on community racial disparities or disparities in access to affordable housing.”
Why would anyone want to suppress this data source? “I’m really not sure, and don’t feel that I can speculate on the possible reasons,” Dr Gomez told Medscape Medical News.
A bigger concern is the intent of H.R.861, which seeks to terminate the EPA, the editorialists point out.
However, Dr Jagai and colleagues continue with their geospatial research right now, using EPA data.
“All the coauthors [from the current study] are still at EPA. I am still working with this team and we are still using the EQI to conduct other research on the impact of cumulative environmental exposures on health outcomes,” she said.
This study was funded in part by the Environmental Protection Agency. The study authors and editorialists have disclosed no relevant financial relationships.