Mapping surface air concentrations from OMI and inferring cancer risks: implications for TEMPO Lei Zhu TEMPO STM 06/01/2017 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, and Viral Shah, Formaldehyde (HCHO) As a Hazardous Air Pollutant: Mapping Surface Air Concentrations from Satellite and Inferring Cancer Risks in the United States, Environ. Sci. Technol., doi: 10.1021/acs.est.7b01356, 2017.

HCHO Finally, some “fresh” air? Let’s start with your hiking experience … HCHO HCHO HCHO HCHO Finally, some “fresh” air? http://www.romanticasheville.com/images2009/chimneys.jpg

According to EPA, HCHO has the largest cancer risk among all 187 HAPs! Cancer risk of HCHO compared to other common hazardous air pollutants (HAPs) According to EPA, HCHO has the largest cancer risk among all 187 HAPs! 57 cancer risk per million Acetaldehyde MetalsPM10All Benzene Naphthalene Formaldehyde 1 mg m-3: 0.077 cancer risks per million [Strum and Scheffe, 2015]

Surface HCHO measurements from EPA sites HCHO [ppb], part per billion Limited EPA sampling network can not properly quantify the health risk posed by ambient HCHO on a national scale EPA HCHO has potential interferences by ozone and NO2

Satellites provide a continuously operating data set since 1995 OMI annual mean HCHO coumns from Isabelle De Smedt (BIRA) TEMPO current instruments single-scene precision GOME, SCIAMACHY, OMI, GOME-2 (A/B), OMPS, TROPOMI, GEMS, TEMPO HCHO column as a proxy for VOC emissions: global background (methane); regional enhancements (biogenic, anthropogenic, and open fires sources)

Mapping surface HCHO concentrations from space is challenging 1. Validation of HCHO retrievals is extremely limited 2013 Aug.-Sep. mean HCHO column Bias=-43% SEAC4RS provides a great opportunity for validation Indirect validation using GEOS-Chem as a inter-comparison platform Satellite retrievals are biased low in the mean by 20–51% [Zhu et al. 2016]

Mapping surface HCHO concentrations from space is challenging 2. Public health implication requires the spatial resolution as fine as possible 2005-2016 JJA For any gird i, it has N(i) overlapped satellite pixels. The mean column is computed as: New oversampling method: Computationally fast Fully uses and appropriately weights the information from all individual satellite observations with a wide range of pixel sizes and column uncertainties Can be improved by adding the spatial response function (Kang Sun, Harvard CFA): possible L2 to L3 regridding method for TEMPO [Zhu et al. 2017]

𝐶 𝑂𝑀𝐼 𝐴 (𝑖)= 𝛺 𝑂𝑀𝐼 𝑆, 𝑁 (𝑖) 𝛾 1 𝐶 𝐺𝐶 𝑆, 𝑁 𝑖 𝛺 𝐺𝐶 𝑆, 𝑁 𝑖 𝛾 2 𝛾 3 (𝑖) Mapping surface HCHO concentrations from space is challenging 3. Relating OMI columns to annual surface concentrations involves many factors Summer noon column GC summer noon surface St. Louis, MO Summer surface HCHO 24h average to noon average ratio (0.70) OMI correction factor (1.67) Brent, AL 𝐶 𝑂𝑀𝐼 𝐴 (𝑖)= 𝛺 𝑂𝑀𝐼 𝑆, 𝑁 (𝑖) 𝛾 1 𝐶 𝐺𝐶 𝑆, 𝑁 𝑖 𝛺 𝐺𝐶 𝑆, 𝑁 𝑖 𝛾 2 𝛾 3 (𝑖) GC summer noon column GC surface annual to summer ratio Pasadena, CA Observed summer surface HCHO diurnal profiles [Zhu et al. 2017]

OMI-derived surface HCHO values match well with observations Mean bias across sites: -2.0% [Zhu et al. 2017]

OMI-derived annual mean surface HCHO and cancer risk we talked about the need to have some error analysis in the annual mean surface HCHO obtained in that way, that we can then propagate to error in cancer risk. Have you looked at this. It would be good to talk about it even if you haven’t done it yet. This number is likely to be larger in a warmer future. 6600–13200 people get cancer (lung and nasopharyngeal) during their lifetime due to ambient HCHO 84–168 cancer cases per year [Zhu et al. 2017]

Implications for TEMPO Public health implication requires the spatial resolution to be as fine as possible – TEMPO may do much better Diurnal variations observed from TEMPO provides more information in deriving long term mean surface concentrations Oversampling approach (with the spatial response function) is a possible L2 to L3 regridding method Need to fix low bias in retrievals SEAC4RS data provides important reference for testing vertical shape factors in retrieval - -expect more from DISCOVER-AQ and KORUS-AQ