Preliminary data released Tuesday by the state Department of Environmental Conservation shows that large particulates in the smoke from last week's fire at the former Bethlehem Steel site created unhealthy to hazardous air quality.
Wind direction and speed determined the air quality in the areas around the fire scene.
At the bocce court at the end of Madison Avenue in Bethlehem Park – about one-third of a mile northeast of the fire site – particulates of 2.5 and 10 microns, respectively, exceeded 300 micrograms per cubic meter at times Thursday afternoon and evening before dropping back to safe levels early Friday morning.
For a couple periods in the afternoon and evening Thursday, the plume of smoke passed over the monitor at the Madison Avenue site, the DEC reported.
The Environmental Protection Agency classifies particulates at 300 micrometers or above as "hazardous" and recommends avoiding outdoor activity.
Microns and micrometers are equivalent units of measurement. Both are equal to one millionth of a meter.
Authorities initially ordered residents in the neighborhood to shelter in place indoors, and then ordered them evacuated Thursday.
Farther away, less than a mile east of the fire scene at Electric and Cleveland avenues, small and larger particulate matter remained at good or moderate levels until about 2:24 a.m. Friday, before it started spiking into the "very unhealthy" category for nearly a two-hour period, according to the data.
That's when the wind shifted the plume of smoke east, the DEC reported.
"The particulate matter concentration at times during these periods were in the hazardous Air Quality Index category," according to a DEC statement.
It added: "These levels were expected and are consistent with instructions that were issued by local first responders at the time to shelter in place, and later to evacuate, and limit exposure to the smoke."
This preliminary data only covers the actual soot from the fire scene in the form of smoke.
The data on chemicals or other components in the smoke are being analyzed with results expected later in the week, Lackawanna Mayor Geoffrey M. Szymanski said Monday during a news conference outside of Lackawanna City Hall.
Residents in the nearby Bethlehem Park neighborhood who were allowed to return to their homes Friday afternoon complained the acrid smell of burning plastic continued to permeate their homes through the weekend. Soot from the fire also covered the neighborhood.
Szymanski said Monday that the city was expected to install several air monitors of its own at "strategic locations" around the neighborhood to gauge air quality.
Demolition continued at the site Tuesday, and firefighters continued turning up and extinguishing hot spots.
Szymanski said the cleanup at and around the fire scene could take months.