The range of indoor perc level was 8 23,000 μg/m3, the median (and geometric mean) was 1,400 μg/m3, and the arithmetic mean was 5,000 μg/m3.
On the other hand, some of the "complaint" buildings had some of the highest perc levels in nonminority, higher income areas.
Work practices (e.g., maintenance of effective vapor barrier/room enclosure, proper use of exhaust fans) can influence fugitive perc emissions, and prior complaints associated with some of the dry cleaner buildings sampled, even though equipment met regulatory requirements, suggests that poor work practices may have contributed to some of the elevated perc levels observed.
Background was considered to be ≤11 μg/m, the 75th percentile of indoor air perc levels detected in homes and offices sampled throughout the United States (Shah and Heyerdahl 1988).
"But by the time you reach the edge of the property, the Perc levels drop off dramatically".
In eight residences in dry cleaner buildings in Hudson County, New Jersey, selected randomly from a list of 82 dry cleaners colocated with residences, indoor air perc levels ranged from 470 to 4,200 μg/m3 when sampled in 1998 (Garetano and Gochfeld 2000).
Visual function assessments (VCS, color vision) and biologic measures of exposure (blood, breath perc levels) have been obtained for participants in the NYC Perc Project.
Second, the six highest perc levels detected, ranging between 695 and 5,000 μg/m3, are in six different dry cleaner buildings located in census block groups characterized as minority or as both minority and low income.
Results from the residential study showed a mean exposure level of 778 microg/m(3) perc in indoor air for a mean of 5.8 years, and that perc levels in breath, blood, and urine were 1-2 ofders of magnitude in excess of background values.
Bias in the selection of households sampled could have influenced the results in the observed direction if recruitment methods reduced the likelihood of including apartments with elevated perc levels in nonminority, higher income neighborhoods.
