Wildfire's move into the suburbs changes what is in the smoke

A burning subdivision emits something different from a burning forest. Vegetation puts out fine particulate matter, PM 2.5, which the World Health Organization associates with premature death, severe damage to respiratory health and cognitive impairment ^[7]. When structures and vehicles burn, Vox reports, the smoke also carries the chemical toxins of urbanization itself: plastic, metal oxides and vehicle fuel ^[8]. Researchers are still learning what that second category does over a lifetime ^[9].

Vox puts 2025 at 5.2 million acres burned across the US, with the current year's total already at 8.5 million before the winter dry seasons that affect parts of the Southwest ^[10]. That is 3.3 million acres more, about 63 percent above last year's full-year figure ^[11]. The 4.2 million acres that made 2020 the worst California fire year on record was one state's total ^[12]. That figure sits on a different scale from the national ones.

The health evidence in this account is about hospital use, and it does not extend to business costs ^[19]. Stanford Health Care in Northern California saw a 12 percent jump in admissions in the weeks following the 2020 fires, and a 43 percent increase in cardiovascular conditions ^[13]. In Oregon that year, smoke-induced asthma-like conditions accounted for 10 percent of emergency room visits ^[14]. A study published in February found that accumulated exposure to wildland smoke was associated with greater hospitalization risk for cardiovascular diseases in older Americans, including irregular heart rhythms and heart failure, even at moderate PM 2.5 levels ^[15].

The changed smoke exposes people in fire zones and in surrounding regions as it drifts outward ^[18]. More than 46 million homes in the continental US, approximately one-third of all homes, sit on the edge of fire-prone wildland ^[16]. If 46 million is a third, the implied national stock is about 138 million homes ^[17].

The two decisions in front of an employer divide by horizon. The one available this quarter is facilities work and it is cheap: filters, a threshold for closing a site or moving people indoors, and a standing way of telling staff what the air is doing. The one that runs for a decade is where buildings go and where staff are expected to live, and Vox's reading of the trend is that urban construction keeps expanding into the wilderness, putting more communities closer to wildfires ^[20].