Impacts of Sugarcane Fires on Air Quality and Public Health in South Florida

Abstract

Background: Preharvest burning of sugarcane is a common agricultural practice in Florida, which produces fine particulate matter [particulate matter (PM) with aerodynamic diameter $\le 2.5\mu m$ (${\mathrm{PM}}_{2.5}$)] that is associated with higher mortality.

Objectives: We estimated premature mortality associated with exposure to ${\mathrm{PM}}_{2.5}$ from sugarcane burning in people age 25 y and above for 20 counties in South Florida.

Methods: We combined information from an atmospheric dispersion model, satellites, and surface measurements to quantify ${\mathrm{PM}}_{2.5}$ concentrations in South Florida and the fraction of ${\mathrm{PM}}_{2.5}$ from sugarcane fires. From these concentrations, estimated mortalities attributable to ${\mathrm{PM}}_{2.5}$ from sugarcane fires were calculated by census tract using health impact functions derived from literature for six causes of death linked to ${\mathrm{PM}}_{2.5}$. Confidence intervals (CI) are provided based on Monte Carlo simulations that propagate uncertainty in the emissions, dispersion model, health impact functions, and demographic data.

Results: Sugarcane fires emitted an amount of primary ${\mathrm{PM}}_{2.5}$ similar to that of motor vehicles in Florida. ${\mathrm{PM}}_{2.5}$ from sugarcane fires is estimated to contribute to mortality rates within the Florida Sugarcane Growing Region (SGR) by 0.4 death per 100,000 people per year (95% CI: 0.3, 1.6 per 100,000). These estimates imply 2.5 deaths per year across South Florida were associated with ${\mathrm{PM}}_{2.5}$ from sugarcane fires (95% CI: 1.2, 6.1), with 0.16 in the SGR (95% CI: 0.09, 0.6) and 0.72 in Palm Beach County (95% CI: 0.17, 2.2).

Discussion: ${\mathrm{PM}}_{2.5}$ from sugarcane fires was estimated to contribute to mortality risk across South Florida, particularly in the SGR. This is consistent with prior studies that documented impacts of sugarcane fire on air quality but did not quantify mortality. Additional health impacts of sugarcane fires, which were not quantified here, include exacerbating nonfatal health conditions such as asthma and cardiovascular problems. Harvesting sugarcane without field burning would likely reduce ${\mathrm{PM}}_{2.5}$ and health burdens in this region. https://doi.org/10.1289/EHP9957.

Figure 1.

(A) Map of the SGR (yellow boundary) and surroundings. Background image is true-color satellite imagery from 10 and 28 January 2021 (Masek et al. 2021). Dark rectangular areas within the SGR are recently burned sugarcane fields. (B) Locations of sugarcane fires and major cities (yellow circles, labeled with names) in peninsular Florida. The SGR is shown in black and colors show population density by ZIP code. Also shown are the U.S. EPA monitoring sites used in analysis (yellow boxes with dots in the center). Note: SGR, sugarcane growing region; U.S. EPA, U.S. Environmental Protection Agency.

Figure 2.

(A) ${\mathrm{PM}}_{2.5}$ concentrations at air quality monitoring sites in Central and South Florida, showing mean concentrations during sugarcane harvest and fire season (October–March) vs. other months outside harvest (April–September). Dots and vertical lines show mean and standard error. Data are averages for 2009–2018, except for Royal Palm Beach, which stopped measurements in 2015. (B) Temporal variability of sugarcane burned area in the SGR and ${\mathrm{PM}}_{2.5}$ concentrations measured in Belle Glade. Data are averaged for 2009–2019 and smoothed with a 3-wk running mean. (C) Mean diurnal cycle of ${\mathrm{PM}}_{2.5}$ concentrations measured in Belle Glade from the U.S. EPA sensor from 2009–2019. (D) Simulated contribution of sugarcane fires to the mean diurnal cycle of ${\mathrm{PM}}_{2.5}$ concentration in Belle Glade and mean diurnal cycle of GOES-16 FRP, which is a proxy for sugarcane fire emissions. The vertical distribution of smoke (B) and GOES-16 FRP are normalized to unit integral. Shading shows standard error of the mean. Note: FRP, fire radiative power; U.S. EPA, U.S. Environmental Protection Agency.

Figure 3.

Example correction of satellite-derived ${\mathrm{PM}}_{2.5}$ (micrograms per cubic meter) to match surface ${\mathrm{PM}}_{2.5}$ concentration measurements in January 2016: (A) uncorrected satellite ${\mathrm{PM}}_{2.5}$; (B) interpolated difference between uncorrected satellite ${\mathrm{PM}}_{2.5}$ and surface measurements (surface minus satellite); (C) corrected satellite-derived ${\mathrm{PM}}_{2.5}$ (micrograms per cubic meter). Black dots show surface measurement sites.

Figure 4.

(A) Multiyear mean of corrected satellite derived ${\mathrm{PM}}_{2.5}$ (micrograms per cubic meter) for the period 2012–2018. (B) Mean difference in surface ${\mathrm{PM}}_{2.5}$ concentrations (micrograms per cubic meter) between sugarcane harvest and outside/other seasons, from corrected satellite-derived ${\mathrm{PM}}_{2.5}$ data for 2009–2018. Positive values in panel B indicate harvest season has higher mean concentration. Black dots show ${\mathrm{PM}}_{2.5}$ surface measurement sites used in this work.

Figure 5.

(A) Vertical distribution of sugarcane smoke in the SGR as a fraction of boundary layer height h, derived from MISR. (B) Mean diurnal cycle of ${\mathrm{PM}}_{2.5}$ from sugarcane fires in Belle Glade simulated for January 2012 with four different plume rise methods. The empirical method is the best estimate, whereas all methods are used for constructing CIs for results. Shading shows the standard error of the mean. Note: CI, confidence interval; MISR, multi-angle imaging SpectroRadiometer; SGR, sugarcane growing region.

Figure 6.

Estimated impacts of sugarcane fires on ${\mathrm{PM}}_{2.5}$ air quality and human health: (A) simulated estimated increase in annual mean ${\mathrm{PM}}_{2.5}$ concentration (micrograms per cubic meter) due to sugarcane fires in 2012–2018; (B) same as panel A with a focus on the SGR; (C) estimated fraction of mortality (six causes of death) attributable to ${\mathrm{PM}}_{2.5}$ exposure from sugarcane fires; (D) estimated mortality rate per 100,000 people per year attributable to sugarcane burning; and (E) same as panel D with a focus on the SGR. Mortality and mortality rate include six causes of death associated with ${\mathrm{PM}}_{2.5}$ from sugarcane fires examined in this study; see Table S9 for county-specific mortality. Light gray shading in panels C–E indicates unpopulated census tracts. Note: SGR, sugarcane growing region.