Back to the future: trace lead in ambient air from wood fuel combustion

Deciding to classify wood as a renewable resource for residential space heating is a contentious issue because it balances a relatively inexpensive fuel, against the public health risks of wood smoke exposure.

To investigate wood fuel emissions as a source of trace lead exposure via ambient air in the northern regions of the United States (US).

Federal Reference Methods filters (n = 182) were obtained from the state of Vermont's Department of Environmental Conservation from Rutland (n = 97) and New Hampshire Department of Environmental Services from Keene (n = 85). Filter samples were collected during the winters of 2011-2016 and analyzed by Energy Dispersive X-ray Fluorescence. Chemical speciation data was compiled from 22 national sites via the Interagency Monitoring of Protected Visual Environments and EPA Chemical Speciation Network (CSN), which were compared to the concentrations of wood smoke emissions observed across northeastern US.

Our evidence indicates a link between wood burning emissions with increased concentrations in particle-bound lead that is associated with wood combustion. Linear regression models in Keene, NH (R² = 0.438) and Rutland, VT (R² = 0.341) indicate moderate agreement between tracers of wood smoke and lead suggesting a common source. On average, lead concentrations ranged from 0.86 ng/m³ in the Rocky Mountains Region to 1.70 ng/m³ in the Southeast Region. We observed varying correlations between lead and potassium across the US, with slight-to-modest agreement (R² = 0.09-0.47) at most sites; the strongest associations were on the Pacific Coast (R² > 0.40). This suggests that a strong relationship between potassium and lead is observed at many nationwide locations.

Wood burning, an activity common in many rural parts of the US, is a likely anthropogenic source of lead introduced into ambient air throughout the northern portion of the US in the winters of 2011-2016. These ambient lead exposures are likely to have long-term adverse public health impacts.

While wood burning promises potential climate benefits in reducing fossil fuels usage, it also poses significant risks related to air pollution and human exposure to toxic substances like lead. These findings suggest that more thorough and better monitoring of biomass burning emissions are necessary to ensure that the transition to wood fuel does not inadvertently cause harm to public health. Hypothesized lead pathway from leaded fuel to wood fuel emissions. Created in BioRender. Henegan, P. (2026) https://BioRender.com/cyi2k2m . Link text: Access lead pathway graphical abstract.