Formaldehyde is more likely to cause cancer than any other toxic chemical in the air.
It is emitted from 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 an industrial or intensive area, the geography and climate of your area can increase your risk of cancer from formaldehyde due to this so-called “secondary formation.”
Read our story → | Read more about our analysis →
About formaldehyde cancer risk and this database
ProPublica analyzed formaldehyde concentrations modeled by the Environmental Protection Agency and released through the agency AirToxScreen database and found that in every US census tract, formaldehyde in the air increased life expectancy the risk of cancer exceeds one disease in every million peoplethe limit below which the agency aims to stay for toxic air pollutants. About 320 million people live in areas where the risk is at least 10 times higher. In other areas, the cancer risk from formaldehyde is even worse. We make this data searchable in this interactive database.
AirToxScreen works by simulating annual emissions (in this case emissions in 2020) along with weather and natural source data to approximate the concentrations of various chemicals in each census block. Although emissions were lower than normal in 2020 due to shutdowns related to COVID-19, we used 2020 data because it is the most recent and detailed available. (Until 2020, AirToxScreen provided results for census tracts, each of which contains many blocks.) The data does not include the risk of formaldehyde in indoor air, which research shows is much higher than outdoors.
The data include two categories of simulated chemical concentrations: environmental concentrations and exposure concentrations. Ambient concentrations are the agency’s estimates of the amount of a chemical in the outdoor air in a tract, while exposure concentrations are the agency’s estimates of how much of the chemical is actually inhaled by a person in the area.
We calculated the additional lifetime risk of cancer by multiplying the concentration of formaldehyde in the AirToxScreen by a number called Inhalation device riskwhich is EPA’s best scientific estimate of the chemical’s carcinogenicity. We used a new inhalation risk block for formaldehyde that was completed in August.
However, even the new IUR is an underestimate. It is based solely on the risk of nasopharyngeal cancer, which is rare. This does not reflect the risk of myelogenous leukemia, a blood cancer that the EPA acknowledged in August is also caused by formaldehyde. The agency calculated the risk of developing myelogenous leukemia, but ultimately decided not to use its estimate because there was no certainty in assigning an exact figure for the amount of the chemical needed to trigger a case of the disease. If the EPA had included the number it calculated, it would have shown that the cancer risk from formaldehyde was about four times higher. Because our analysis is based on EPA’s IUR, this database also underestimates the cancer risk from formaldehyde.
Some census units contain caveats that EPA has published since the release of AirToxScreen. The EPA would not provide guidance on how to adjust our results for these caveats and said it is recalculating the cancer risk in these areas. Some blocks appear to be at very high risk because wildfires occurred in or near them in 2020, and emissions in 2020 were used to calculate lifetime risks. These blocks may not necessarily have as high risks as shown, but according to the EPA“Climate change has already led to an increase in the length of the wildfire season, the frequency of wildfires, and the area burned. This may affect future risks.” Blocks with extremely high wildfire risk have an EPA notice on their results pages.
Sources: EPA AirToxScreen 2020, EPA’s Integrated Risk Information System
Jeff Frankl contributed to the design and development.
