Formaldehyde (HCHO) As a Hazardous Air Pollutant: Mapping Surface Air Concentrations from Satellite and Inferring Cancer Risks in the United States

Lei Zhu, Daniel J. Jacob, Frank N. Keutsch, Loretta J. Mickley, Richard Scheffe, Madeleine Strum, Gonzalo González Abad, Kelly Chance, Kai Yang, Bernhard Rappenglück, Dylan B Millet, Munkhbayar Baasandorj, Lyatt Jaeglé, Viral Shah

Research output: Contribution to journalArticlepeer-review

82 Scopus citations


Formaldehyde (HCHO) is the most important carcinogen in outdoor air among the 187 hazardous air pollutants (HAPs) identified by the U.S. Environmental Protection Agency (EPA), not including ozone and particulate matter. However, surface observations of HCHO are sparse and the EPA monitoring network could be prone to positive interferences. Here we use 2005-2016 summertime HCHO column data from the OMI satellite instrument, validated with high-quality aircraft data and oversampled on a 5 × 5 km2 grid, to map surface air HCHO concentrations across the contiguous U.S. OMI-derived summertime HCHO values are converted to annual averages using the GEOS-Chem chemical transport model. Results are in good agreement with high-quality summertime observations from urban sites (-2% bias, r = 0.95) but a factor of 1.9 lower than annual means from the EPA network. We thus estimate that up to 6600-12 500 people in the U.S. will develop cancer over their lifetimes by exposure to outdoor HCHO. The main HCHO source in the U.S. is atmospheric oxidation of biogenic isoprene, but the corresponding HCHO yield decreases as the concentration of nitrogen oxides (NOx ≡ NO + NO2) decreases. A GEOS-Chem sensitivity simulation indicates that HCHO levels would decrease by 20-30% in the absence of U.S. anthropogenic NOx emissions. Thus, NOx emission controls to improve ozone air quality have a significant cobenefit in reducing HCHO-related cancer risks.

Original languageEnglish (US)
Pages (from-to)5650-5657
Number of pages8
JournalEnvironmental Science and Technology
Issue number10
StatePublished - May 16 2017

Bibliographical note

Funding Information:
This work was supported by the NASA Earth Science Division. Funding for the SLAQRS measurements was provided by NSF (Grant #1148951). We thank Noelle Selin for valuable discussions on HCHO cancer risks.

Publisher Copyright:
© 2017 American Chemical Society.


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