PEW Technical Report, September 2000

In 2000, the Pew Environmental Health Commission published the technical report “America’s Environmental Health Gap: Why the Country Needs a Nationwide Health Tracking Network.” The Pew report spelled out the same difficulties in linking environmental toxins to resulting health conditions that our own research discovered:

“We know there are pollutants entering our air and water each year with suspected or known adverse effects on the health of our communities. What we are limited in knowing is if there is a link between that pollution and the increases we are seeing in chronic diseases because we aren’t tracking environmental health factors” (p. 2).

Environmental health in the U.S. since the 1950s had evolved into two tracks. On one track were state environmental agencies and the Environmental Protection Agency (EPA, established in 1970), which used a regulatory approach that was primarily structured to characterize cancer risks by studying single hazards, largely based on animal toxicology tests. On the other track were public health agencies that used a tracking-based population approach, which relied “upon hazard, exposure, and health outcome tracking data to guide decisions” (Pew report, p. 38).

The Pew report emphasizes that tracking is necessary within each component: Hazard Tracking, including monitoring of air and water quality; Exposure Tracking, including biological monitoring of human exposures; and Health Outcome Tracking, including cancer registries and the publication of cancer incidence tables (p. 29-35).

Cancer Statistics Reporting and Limitations

From 2002-2005, the Centers for Disease Control and Prevention (CDC) responded to the hazard, exposure, and health outcome tracking needs expressed in the Pew Report, creating the Environmental Public Health Tracking Program. The purpose of the program is to deliver information regarding environmentally-based health issues. in 2009, the program launched a dynamic, web-based system of data and information known as the Environmental Public Health Tracking Network.

The Tracking Program explains several of the conundrums facing public health officials in attempting to connect hazards to cancer. These include the fact that “cancer is a diverse group of diseases…caused by both external and internal risk factors”; and that “while risk factors for some cancers have been determined, the etiology of many cancer types is not as well-established”; and that “few community-level environmental exposures have been well studied” (Indicators and Data, Rationale).

The Tracking Program also addresses the limitations in using the statistical subdivisions of counties known as census tracts for cancer incidence reporting, due to reliability and confidentiality concerns for communities that have small populations. The Tracking Program’s solution is to aggregate census tracts to a specified minimum population level of 5,000 (Tracking Program, GitHub).

The Tracking Program informs readers about caution in interpreting cancer statistics (Indicators and Data, Limitations of the Measures). These limitations include that:

• Counts and rates are calculated based on residential address at time of diagnosis. No information is available on prior residences.
• Geocoding accuracy, level of geocoding, and geocoding completeness may vary by time and space. This could potentially create geographically non-random errors in calculated rates of cancer.
• No personal exposure information will be available, including smoking history, diet, lifestyle, or history of cancer.
• Case counts less than 16 and rates based on counts less than 16 are suppressed to protect confidentiality and to prevent misinterpretation of unstable rates. Additionally, case counts and rates are suppressed in geographies with 100 or fewer persons.
• No information will be available on the latency of cancer cases.

In this cancer mapping project report, I will attempt to explore some of these limitations in relation to my own barriers and challenges while trying to connect the dots between environmental hazards and cancer in our small town.

The professionals that record and report on cancer statistics provide a remarkable service in our efforts to understand, prevent, and treat cancer. We need to supplement cancer incidence information with other methods, such as longitudinal and case-control studies, to fill in the missing pieces between community hazard information and cancer statistics.