Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Exposures and behavioural responses to wildfire smoke

Abstract

Pollution from wildfires constitutes a growing source of poor air quality globally. To protect health, governments largely rely on citizens to limit their own wildfire smoke exposures, but the effectiveness of this strategy is hard to observe. Using data from private pollution sensors, cell phones, social media posts and internet search activity, we find that during large wildfire smoke events, individuals in wealthy locations increasingly search for information about air quality and health protection, stay at home more and are unhappier. Residents of lower-income neighbourhoods exhibit similar patterns in searches for air quality information but not for health protection, spend less time at home and have more muted sentiment responses. During smoke events, indoor particulate matter (PM2.5) concentrations often remain 3–4× above health-based guidelines and vary by 20× between neighbouring households. Our results suggest that policy reliance on self-protection to mitigate smoke health risks will have modest and unequal benefits.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Trends in smoke exposure across the United States.
Fig. 2: Behavioural responses to wildfire smoke exposure.
Fig. 3: Smoke salience does not differ, but other responses do differ, among more and less wealthy populations.
Fig. 4: Infiltration rates decline strongly with outdoor PM2.5 concentration during both fire and non-fire periods, but not with income, and they differ greatly across households, resulting in extreme differences in indoor exposure during wildfires.

Similar content being viewed by others

Data availability

The data to replicate all the results in the main text and supplementary material are available at https://github.com/echolab-stanford/wildfire-exposure-behavior-public.

Code availability

The code to replicate all the results in the main text and supplementary material is available at https://github.com/echolab-stanford/wildfire-exposure-behavior-public.

References

  1. Landrigan, P. J. et al. The Lancet Commission on pollution and health. Lancet 391, 462–512 (2018).

    Article  PubMed  Google Scholar 

  2. Carleton, T. A. & Hsiang, S. M. Social and economic impacts of climate. Science 353, aad9837 (2016).

    Article  PubMed  Google Scholar 

  3. Aizer, A., Currie, J., Simon, P. & Vivier, P. Do low levels of blood lead reduce children’s future test scores? Am. Econ. J. Appl. Econ. 10, 307–41 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  4. Deryugina, T., Miller, N., Molitor, D. & Reif, J. Geographic and socioeconomic heterogeneity in the benefits of reducing air pollution in the United States. Environ. Energy Policy Econ. 2, 157–189 (2021).

    Article  PubMed  PubMed Central  Google Scholar 

  5. Burke, M., Hsiang, S. M. & Miguel, E. Global non-linear effect of temperature on economic production. Nature 527, 235–239 (2015).

    Article  CAS  PubMed  Google Scholar 

  6. Grönqvist, H., Nilsson, J. P. & Robling, P.-O. Understanding how low levels of early lead exposure affect children’s life trajectories. J. Polit. Econ. 128, 3376–3433 (2020).

    Article  Google Scholar 

  7. US Department of Health and Human Services Theory at a Glance: A Guide for Health Promotion Practice (National Cancer Institute, 2005).

  8. Greenstone, M. & Jack, B. K. Envirodevonomics: a research agenda for an emerging field. J. Econ. Lit. 53, 5–42 (2015).

    Article  Google Scholar 

  9. Abatzoglou, J. T. & Williams, A. P. Impact of anthropogenic climate change on wildfire across western US forests. Proc. Natl Acad. Sci. USA 113, 11770–11775 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Burke, M. et al. The changing risk and burden of wildfire in the United States. Proc. Natl Acad. Sci. USA 118, e2011048118 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. Hurteau, M. D., Westerling, A. L., Wiedinmyer, C. & Bryant, B. P. Projected effects of climate and development on California wildfire emissions through 2100. Environ. Sci. Technol. 48, 2298–2304 (2014).

    CAS  PubMed  Google Scholar 

  12. Liu, J. C. et al. Particulate air pollution from wildfires in the western US under climate change. Climatic Change 138, 655–666 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  13. Goss, M. et al. Climate change is increasing the likelihood of extreme autumn wildfire conditions across California. Environ. Res. Lett. 15, 094016 (2020).

    Article  Google Scholar 

  14. Reid, C. E. et al. Critical review of health impacts of wildfire smoke exposure. Environ. Health Perspect. 124, 1334–1343 (2016).

    Article  PubMed  PubMed Central  Google Scholar 

  15. Cascio, W. E. Wildland fire smoke and human health. Sci. Total Environ. 624, 586–595 (2018).

    Article  CAS  PubMed  Google Scholar 

  16. Xu, R. et al. Wildfires, global climate change, and human health. N. Engl. J. Med. 383, 2173–2181 (2020).

    Article  PubMed  Google Scholar 

  17. Zhou, X. et al. Excess of COVID-19 cases and deaths due to fine particulate matter exposure during the 2020 wildfires in the United States. Sci. Adv. 7, eabi8789 (2021).

    Article  PubMed  PubMed Central  Google Scholar 

  18. Heft-Neal, S., Driscoll, A., Yang, W., Shaw, G. & Burke, M. Associations between wildfire smoke exposure during pregnancy and risk of preterm birth in California. Environ. Res. 203, 111872 (2021).

    Article  PubMed  Google Scholar 

  19. Santana, F. N., Gonzalez, D. J. & Wong-Parodi, G. Psychological factors and social processes influencing wildfire smoke protective behavior: insights from a case study in Northern California. Clim. Risk Manage. 34, 100351 (2021).

    Article  Google Scholar 

  20. Rappold, A. et al. Smoke Sense initiative leverages citizen science to address the growing wildfire-related public health problem. GeoHealth 3, 443–457 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Reid, C. E. et al. Differential respiratory health effects from the 2008 northern California wildfires: a spatiotemporal approach. Environ. Res. 150, 227–235 (2016).

    Article  CAS  PubMed  Google Scholar 

  22. Kondo, M. C. et al. Meta-analysis of heterogeneity in the effects of wildfire smoke exposure on respiratory health in North America. Int. J. Environ. Res. Public Health 16, 960 (2019).

    Article  PubMed Central  Google Scholar 

  23. Wen, J. & Burke, M. Wildfire smoke exposure worsens learning outcomes. Preprint at EarthArXiv https://doi.org/10.31223/X52H06 (2021).

  24. Wildfire Smoke: A Guide for Public Health Officials, 2019 Revision (US Environmental Protection Agency, 2019).

  25. Pellert, M., Metzler, H., Matzenberger, M. & Garcia, D. Validating daily social media macroscopes of emotions. Preprint at arXiv https://doi.org/10.48550/arXiv.2108.07646 (2021).

  26. Baylis, P. Temperature and temperament: evidence from Twitter. J. Public Econ. 184, 104161 (2020).

    Article  Google Scholar 

  27. Baylis, P. et al. Weather impacts expressed sentiment. PLoS ONE 13, e0195750 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  28. Hutto, C. & Gilbert, E. VADER: a parsimonious rule-based model for sentiment analysis of social media text. Proc. Int. AAAI Conf. Web Soc. Media 8, 216–225 (2014).

    Google Scholar 

  29. Wang, Z., Ye, X. & Tsou, M.-H. Spatial, temporal, and content analysis of Twitter for wildfire hazards. Nat. Hazards 83, 523–540 (2016).

    Article  Google Scholar 

  30. Sachdeva, S., McCaffrey, S. & Locke, D. Social media approaches to modeling wildfire smoke dispersion: spatiotemporal and social scientific investigations. Inform. Commun. Soc. 20, 1146–1161 (2017).

    Article  Google Scholar 

  31. Choi, H. & Varian, H. Predicting the present with Google Trends. Econ. Rec. 88, 2–9 (2012).

    Article  Google Scholar 

  32. Goel, S., Hofman, J. M., Lahaie, S., Pennock, D. M. & Watts, D. J. Predicting consumer behavior with web search. Proc. Natl Acad. Sci. USA 107, 17486–17490 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  33. Liang, Y. et al. Wildfire smoke impacts on indoor air quality assessed using crowdsourced data in California. Proc. Natl Acad. Sci. USA 118, e2106478118 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Miller, K. A. et al. Estimating ambient-origin PM2.5 exposure for epidemiology: observations, prediction, and validation using personal sampling in the Multi-Ethnic Study of Atherosclerosis. J. Expo. Sci. Environ. Epidemiol. 29, 227–237 (2019).

    Article  CAS  PubMed  Google Scholar 

  35. Shrestha, P. M. et al. Impact of outdoor air pollution on indoor air quality in low-income homes during wildfire seasons. Int. J. Environ. Res. Public Health 16, 3535 (2019).

    Article  CAS  PubMed Central  Google Scholar 

  36. Uejio, C. et al. Summer indoor heat exposure and respiratory and cardiovascular distress calls in New York City, NY, US. Indoor Air 26, 594–604 (2016).

    Article  CAS  PubMed  Google Scholar 

  37. Ferguson, L. et al. Exposure to indoor air pollution across socio-economic groups in high-income countries: a scoping review of the literature and a modelling methodology. Environ. Int. 143, 105748 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  38. Bi, J., Wallace, L. A., Sarnat, J. A. & Liu, Y. Characterizing outdoor infiltration and indoor contribution of PM2.5 with citizen-based low-cost monitoring data. Environ. Pollut. 276, 116763 (2021).

    Article  CAS  PubMed  Google Scholar 

  39. Allen, R. W. et al. Modeling the residential infiltration of outdoor PM2.5 in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). Environ. Health Perspect. 120, 824–830 (2012).

    Article  PubMed  PubMed Central  Google Scholar 

  40. Krebs, B., Burney, J., Zivin, J. G. & Neidell, M. Using crowd-sourced data to assess the temporal and spatial relationship between indoor and outdoor particulate matter. Environ. Sci. Technol. 55, 6107–6115 (2021).

    Article  CAS  PubMed  Google Scholar 

  41. Lu, J. G. Air pollution: a systematic review of its psychological, economic, and social effects. Curr. Opin. Psychol. 32, 52–65 (2020).

    Article  PubMed  Google Scholar 

  42. Rappold, A. G. et al. Cardio-respiratory outcomes associated with exposure to wildfire smoke are modified by measures of community health. Environ. Health 11, 71 (2012).

    Article  PubMed  PubMed Central  Google Scholar 

  43. Brulle, R. J. & Pellow, D. N. Environmental justice: human health and environmental inequalities. Annu. Rev. Public Health 27, 103–124 (2006).

    Article  PubMed  Google Scholar 

  44. Hajat, A. et al. Air pollution and individual and neighborhood socioeconomic status: evidence from the Multi-Ethnic Study of Atherosclerosis (MESA). Environ. Health Perspect. 121, 1325–1333 (2013).

    Article  PubMed  PubMed Central  Google Scholar 

  45. Zheng, S., Wang, J., Sun, C., Zhang, X. & Kahn, M. E. Air pollution lowers Chinese urbanites’ expressed happiness on social media. Nat. Hum. Behav. 3, 237–243 (2019).

    Article  PubMed  Google Scholar 

  46. deSouza, P. & Kinney, P. L. On the distribution of low-cost PM2.5 sensors in the US: demographic and air quality associations. J. Expo. Sci. Environ. Epidemiol. 31, 514–524 (2021).

    Article  PubMed  Google Scholar 

  47. Sun, C., Kahn, M. E. & Zheng, S. Self-protection investment exacerbates air pollution exposure inequality in urban China. Ecol. Econ. 131, 468–474 (2017).

    Article  Google Scholar 

  48. Currie, J., Voorheis, J. & Walker, R. What caused racial disparities in particulate exposure to fall? New evidence from the Clean Air Act and satellite-based measures of air quality. Preprint at National Bureau of Economic Research https://doi.org/10.3386/w26659 (2020).

  49. Di, Q. et al. An ensemble-based model of PM2.5 concentration across the contiguous United States with high spatiotemporal resolution. Environ. Int. 130, 104909 (2019).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  50. Reid, C. E., Considine, E. M., Maestas, M. M. & Li, G. Daily PM2.5 concentration estimates by county, zip code, and census tract in 11 western states 2008–2018. Sci. Data 8, 112 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  51. O’Dell, K., Ford, B., Fischer, E. V. & Pierce, J. R. Contribution of wildland-fire smoke to US PM2.5 and its influence on recent trends. Environ. Sci. Technol. 53, 1797–1804 (2019).

    Article  PubMed  Google Scholar 

  52. Grainger, C. & Schreiber, A. Discrimination in ambient air pollution monitoring? AEA Pap. Proc. 109, 277–282 (2019).

    Article  Google Scholar 

  53. Fowlie, M., Rubin, E. & Walker, R. Bringing satellite-based air quality estimates down to earth. AEA Pap. Proc. 109, 283–288 (2019).

    Article  Google Scholar 

  54. Wooldridge, J. M. Introductory Econometrics: A Modern Approach (Cengage Learning, 2015).

  55. Massicotte, P. & Eddelbuettel, D. gtrendsR, R package version 1.4.8.9000 https://github.com/PMassicotte/gtrendsR (2021).

  56. Characteristics of People by Language Spoken at Home 2019: 2015–2019 American Community Survey 5-Year Estimates (US Census Bureau, 2020).

  57. Squire, R. F. Measuring and correcting sampling bias in SafeGraph patterns for more accurate demographic analysis. Safegraph https://www.safegraph.com/blog/measuring-and-correcting-sampling-bias-for-accurate-demographic-analysis (2019).

  58. Weill, J. A., Stigler, M., Deschenes, O. & Springborn, M. R. Social distancing responses to COVID-19 emergency declarations strongly differentiated by income. Proc. Natl Acad. Sci. USA 117, 19658–19660 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  59. Valdez, D., Ten Thij, M., Bathina, K., Rutter, L. A. & Bollen, J. Social media insights into US mental health during the COVID-19 pandemic: longitudinal analysis of Twitter data. J. Med. Internet Res. 22, e21418 (2020).

    Article  PubMed  PubMed Central  Google Scholar 

  60. Morawska, L. et al. How can airborne transmission of COVID-19 indoors be minimised? Environ. Int. 142, 105832 (2020).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  61. Meager, R. Understanding the average impact of microcredit expansions: a Bayesian hierarchical analysis of seven randomized experiments. Am. Econ. J. Appl. Econ. 11, 57–91 (2019).

    Article  Google Scholar 

  62. Vivalt, E. How much can we generalize from impact evaluations? J. Eur. Econ. Assoc. 18, 3045–3089 (2020).

    Article  Google Scholar 

  63. 2019 Tiger/Line Shapefiles (US Census Bureau, 2019).

  64. GADM Data (GADM, 2018).

Download references

Acknowledgements

We thank the Robert Wood Johnson Foundation and Stanford’s Center for Population Health Sciences for funding (M.B., S.H.-N., J.L. and A.D.), SafeGraph for data access, Stanford University and the Stanford Research Computing Center for computational resources and support, and members of the ECHOLab and seminar participants at Cornell, Columbia, MIT, Stanford, UC Berkeley and UC Santa Barbara for helpful comments. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Author information

Authors and Affiliations

Authors

Contributions

All authors contributed to the conception and design of the study. S.H.-N., J.L., A.D., J.W. and M.L.C. constructed the smoke data. J.L. and A.D. constructed the Google search data. P.B. constructed the Twitter dataset. M.S. and J.A.W. constructed the mobility dataset. S.H.-N. constructed the PurpleAir dataset. M.B. and S.H.-N. led the econometric analysis. All authors contributed to analysing the results and writing the paper.

Corresponding author

Correspondence to Marshall Burke.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Human Behaviour thanks Priyanka deSouza, Francesca Dominici and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Counties included in analyses that use EPA pollution monitors, and correlation in smoke PM2.5 between monitor pairs as a function of distance between monitors.

a. Counties in red are those with EPA pollution monitors from which we construct smoke PM2.5 measures for the behavioral analyses. b Colors depict a heatmap of the 85,102 pairwise correlations, with lighter colors depicting areas with more data and shown in legend at right; solid black line is the median correlation at each distance. Sample is restricted to stations with at least 1000 days of data. Mean width of counties in our data is 55 km, and mean width of metro areas is 228 km. Source for a: US Census Bureau.

Extended Data Fig. 2 Time spent indoors at home in America.

Data are from repeated rounds of the American Time Use Survey. Top panels show data by average income, age, season, and race/ethnicity. Bottom map shows averages by state across survey rounds. Source for e: US Census Bureau.

Extended Data Fig. 3 Effect of smoke PM2.5 on different mobility measures, and heterogeneity by income.

a Percent of mobile phones estimated to be completely at home on a given day at the US county level, 2019–2020. Black lines are regression point estimates from spline fits conditional on fixed effects, with shaded areas showing bootstrapped 95% confidence intervals. Number of observations in each regression is shown in upper left corner of each panel. Histograms at the bottom show the log distribution of smoke PM2.5 exposure in each sample. b Same but for % fully away from home on that day. c-d Effect of smoke PM2.5 on mobility as a function of income. Lines show the marginal effect of a heavy smoke exposure (50ug smoke PM2.5 on that day) on percent of individuals completely at home on that day (c) or completely away from home (d), as a function of median household income in that county. Colors represent models run with either date fixed effects (blue) or state-by-date fixed effects (orange). Dark lines show regression point estimates, shaded area the bootstrapped 95% CI.

Extended Data Fig. 4 Exposure to average and acute smoke PM2.5 at the county level does not differ systematically by income.

Daily smoke PM2.5 exposures by income decile across US counties, 2006-2020. Dots represent daily observations where smoke PM2.5 was non-zero. Plot is truncated at 300ug for clarity; not plotted are 71 days (0.001% of the sample) in which smoke PM2.5 exceeded 300. Statistics at right show the percent of observations across the study period with daily smoke PM2.5 observations above the listed value.

Extended Data Fig. 5 Higher income US census tracts are more likely to have PurpleAir monitors.

Grey bars show the distribution of tract-level median household income across all US census tracts in the contiguous US, red bars the income in tracts with at least one outdoor PurpleAir sensor, and blue bars the income in tracts with at least one indoor PurpleAir sensor. Vertical lines give the median of each distribution.

Extended Data Fig. 6 Infiltration estimates are highly correlated across alternate statistical models and methods of deriving PM2.5 concentrations from Purple Air data.

Correlation between infiltration estimates from statistical models with different lag structures and different PM2.5 concentration estimates (see Supplementary Table 11 for details). 1a is our preferred specification presented in the main results.

Extended Data Fig. 7 Understanding variation in household-specific infiltration estimates.

a Posterior estimates of monitor-specific infiltration rates from a Bayesian hierarchical model are very similar to “raw” estimates from our monitor-specific time-series regressions, indicating that true heterogeneity rather than sampling noise is what is driving observed differences in estimated infiltration. b Ability of random forest (RF) or gradient boosted trees (GBT) model to explain variation (r2) in infiltration across monitors remains low; models use predictors in (c). c For each predictor, we calculate the effect on infiltration of moving from the 5th to the 95th percentile of that predictor in the test dataset, holding the other predictors constant at their average value in the test dataset; estimates are shown for RF and GBT models and for four alternate spatial buffers used to construct housing predictors. Housing Index is constructed by averaging standardized values of home value, number of stories, number of baths, number of bedrooms, height, and area. A/C measures the inverse distance weighted proportion of matched CoreLogic houses that have air conditioning. Median Income is the median household income in the Census tract population. Race variables (i.e. all demographic covariates except Hispanic) are measured among the non-Hispanic/Latino population. AI/AN stands for American Indian and Alaska Native. NHPI stands for Native Hawaiian and other Pacific Islander. HDD and CDD stand for heating degree days and cooling degree days, respectively. d Range of household-level infiltration estimates for the full sample and for sub-samples when behavior (ie opening/closing of doors, use of air purifier) is expected to matter less: when it’s raining, nighttime, and periods when it is cold ( < 10C) and low PM2.5 ( < 30μg/m3). e-f during periods when behavioral factors are more likely minimized, infiltration varies more strongly with income and housing age.

Extended Data Fig. 8 Monitor-specific infiltration estimates using indoor/outdoor ratios versus regression-based approaches.

I/O estimates are only modestly correlated with our preferred regression-based estimates that measure the marginal effect on indoor PM2.5 concentrations of a unit increase in outdoor concentrations. For each monitor I/O ratio was calculated across all observations with hourly indoor PM2.5 less or equal to outdoor PM2.5. δI/δO was estimated as described in Methods.

Extended Data Fig. 9 Outdoor and indoor PM2.5 concentrations on a smoke day in CA.

Very similar outdoor PM2.5 concentrations during a smoke event on Aug 20th, 2021 over a high-income area of the peninsular Bay Area were associated with widely varying contemporaneous indoor PM2.5 concentrations. © OpenStreetMap contributors.

Extended Data Fig. 10 Variation in indoor PM2.5 across monitors with similar outdoor PM2.5 during the Aug/Sep 2020 smoke event in the Bay Area.

Each dot is average outdoor PM2.5 and average indoor PM2.5 for an individual monitor in the Bay Area over the Aug/Sep 2020 smoke event, with monitors grouped into 5 μg/m3bins based on outdoor exposure. Numbers at top show the number of monitors in each bin (black), and the ratio of maximum to minimum indoor PM2.5 across monitors within each outdoor PM2.5 bin (red). Monitors with average outdoor PM2.5 exposures within 5 μg/m3of each other experienced > 20x differences in indoor PM2.5 exposures.

Supplementary information

Supplementary Information

Supplementary Methods and Tables 1–12.

Reporting Summary.

Peer Review File.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Burke, M., Heft-Neal, S., Li, J. et al. Exposures and behavioural responses to wildfire smoke. Nat Hum Behav 6, 1351–1361 (2022). https://doi.org/10.1038/s41562-022-01396-6

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue date:

  • DOI: https://doi.org/10.1038/s41562-022-01396-6

This article is cited by

Search

Quick links

Nature Briefing Anthropocene

Sign up for the Nature Briefing: Anthropocene newsletter — what matters in anthropocene research, free to your inbox weekly.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing: Anthropocene