Wood burning reintroduces lead pollution into air, US scientists find

Wood heating is reintroducing lead into the air of local communities and homes, a systematic investigation by academics has found.

Overwhelming evidence of lead’s neurotoxicity led to its ban as a petrol additive more than 25 years ago. The University of Massachusetts Amherst researchers analyzed particle pollution samples from five suburban and rural towns in the northeastern US, searching for tiny potassium particles released when wood is burned, along with lead-containing particles.

Samples collected over seven winters revealed consistent associations between potassium and lead. In four of the five towns, increased wood burning particles correlated with higher airborne lead levels, showing clear linear relationships.

Prof Richard Peltier, the study’s senior author, said: “For the most part, wood burning produces significant amounts of particle air pollution, and a small but measurable fraction of this is a powerful neurotoxicant.”

Tricia Henegan, a PhD student at UMass Amherst and the study’s first author, said: “Wood fuels have been a popular choice in much of the world. We were concerned that there were harmful elements that place the public at risk. It turns out that we were right.”

The research team extended the project to 22 additional towns across the United States. The strength of the lead-potassium relationship varied by location, with the strongest associations observed in the Rocky Mountains. After accounting for temperature effects, moderate to strong correlations in their analysis reinforced the conclusion that wood burning contributed the additional lead.

Measured lead concentrations fell below US legal limits, but researchers emphasize that any lead exposure is harmful.

Lead was used globally as a petrol additive beginning in the 1920s, eventually accumulating in oceans, soils and human bodies. Industry systematically suppressed evidence of its harms. Today, scientists acknowledge lead causes damage at all life stages and originates from multiple sources.

Although lead levels remain below legal thresholds, UK cities routinely detect lead particles in winter when wood burning increases. Officials typically attribute this to waste wood coated with old lead paint, but the UMass Amherst study suggests the metal originates within the wood itself, meaning any wood burning could elevate neighborhood and indoor exposure.

Henegan said: “The most logical answer is that it comes from uptake in the soil, probably riding along with the nutrients and water that trees need. Once in the tree, it deposits in the tree’s tissues and remains until that tree is burned.”

Additional research on both old and modern stoves indicates combustion temperatures are high enough for lead to become part of the smoke. A 2003 study in rural Sweden found higher lead levels in homes using wood heating compared to those that did not.

Henegan said: “The use of wood as an energy source is a relic of the past, one that should not be relived if given a choice. Although wood fuel use can feel nostalgic, it does have negative consequences on air quality, and therefore public health.”