Formaldehyde causes more cancers than any other toxic chemical in the air. They are emitted by cars, trucks, airplanes, industrial facilities, and many other sources. It is also formed in the atmosphere when other chemicals combine in the presence of sunlight. Even if you don’t live in a high-traffic or industrial area, your area’s geography and climate may increase your risk of cancer from formaldehyde due to so-called “secondary formation.”
Read our story → |Read more about our analysis →
About the cancer risk caused by formaldehyde and this database
ProPublica analyzed formaldehyde concentrations modeled by the Environmental Protection Agency and published through the agency’s AirToxScreen database and found that in every populated census block in the United States, formaldehyde in the air We found that it increases your lifetime cancer risk by more than the 1 in 1 cancer incidence rate. Limits that government agencies aim to keep below on toxic air pollutants. Approximately 320 million people live in areas where the risk is at least 10 times higher. In other regions, the cancer risk from formaldehyde is even worse. We’re making that data searchable in this interactive database.
AirToxScreen models a year’s worth of emissions (in this case, 2020 emissions) along with weather data and natural sources to approximate the concentrations of various chemicals in each census block. Although emissions in 2020 were likely lower than previous years due to COVID-19 shutdowns, we used 2020 data because it is the latest and most detailed data available. (Prior to 2020, AirToxScreen provided results by census tract, but each tract contained many blocks.) This data includes: is not included, but studies have shown it to be much higher than outdoors.
The data includes two categories of modeled chemical concentrations: ambient and exposure concentrations. Ambient concentration is a government agency’s estimate of the amount of a chemical in the outdoor air in an area, whereas exposure concentration is how much of a chemical would realistically be inhaled by humans in the area. These are government agency estimates.
We calculated the incremental lifetime cancer risk by multiplying AirToxScreen’s formaldehyde exposure concentration by a number called the inhalation unit risk, which is the EPA’s best scientific estimate of a chemical’s carcinogenic potential. We used the new inhalation device risks for formaldehyde that were finalized in August.
But even the new IUR is undervalued. This is based solely on the risk of nasopharyngeal cancer, which is rare. This does not reflect the risk of myeloid leukemia, a blood cancer that the EPA also acknowledged in August to be caused by formaldehyde. The agency calculated the risk of developing myeloid leukemia, but ultimately decided not to use that estimate because it was not confident in assigning an accurate number to the amount of chemicals needed to cause the disease. If the EPA had included the numbers it calculated, it would have shown that the cancer risk from formaldehyde is approximately four times higher. Because our analysis is based on EPA’s IUR, this database also underestimates the cancer risk from formaldehyde.
Certain census blocks include warnings published by EPA after AirToxScreen was released. EPA said it does not plan to provide guidance on how to adjust results to account for these warnings and is recalculating cancer risks in these areas. Some blocks appear to be at very high risk because wildfires occurred in or near the block in 2020 and 2020 emissions were used to calculate lifetime risk. While these blocks are not necessarily at as high a risk as indicated, according to the EPA, “climate change is already increasing the length of wildfire seasons, the frequency of wildfires, and the area burned. This may affect future risks.” Blocks that are at very high risk from wildfires will have an EPA advisory on the results page.
Source: EPA AirToxScreen 2020, EPA Integrated Risk Information System
Jeff Frankl contributed design and development.
