Wildfire smoke exposure was linked to higher head and neck cancer incidence, most for larynx

Design

Retrospective ecological cohort with distributed lag non-linear model

Population

US SEER head and neck cancer incidence by county, 2016-2022

Primary outcome

Cumulative head and neck cancer incidence by wildfire PM2.5 exposure

Effect

cRR 1.06 (1.04-1.09) per exceedance day; larynx cRR 1.13 (1.07-1.19)

Using SEER incidence data from 2016 to 2022 and county-level estimates of wildfire-specific fine particulate matter (Laryngoscope, 13 October 2026), investigators modelled exposure over lags of up to 10 years, adjusting for tobacco, alcohol, diet, exercise, sexual behaviour and demographics.

More smoke was associated with higher cumulative head and neck cancer incidence: a cumulative relative risk of 1.06 (95% CI 1.04-1.09) per additional smoke exceedance day, and 1.41 (1.24-1.60) for any annual exposure. By subsite, the largest association was for larynx (1.13 per exceedance day), with smaller associations for oropharynx (1.09) and oral cavity (1.03). Associations held for p16-positive and p16-negative oropharyngeal tumours.

This is ecological, county-level data, and individual exposure was not measured. It adds wildfire smoke to the list of airborne exposures worth asking about, and it matters in places where seasonal biomass burning is a familiar part of life.

• Ask about long-term smoke exposure, including wildfire and biomass smoke, in the occupational and environmental history.
• Keep tobacco and alcohol as the first targets; this association is much smaller than theirs.
• Do not lower the threshold for laryngoscopy on smoke exposure alone; persistent hoarseness remains the trigger.
• Seasonal crop-residue burning exposes many people in north India to similar smoke, though Indian data were not studied.

Why it matters

It suggests a growing environmental exposure may contribute to cancers clinicians usually attribute only to personal habits.

Don't overread it

County-level ecological data cannot show that smoke caused any individual's cancer.

The statistics, in plain English

A cumulative relative risk of 1.06 per exceedance day means about 6% higher incidence for each extra smoky day, summed over a decade of lag. Ecological studies are prone to confounding by other differences between counties.

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