an airborne toxics control measure
(ATCM) to reduce formaldehyde emissions from composite wood products.
Although the measure went into effect
Jan. 1, 2009, retailers have until Dec. 31,
2010, to “sell through” their existing inventory. (For more information, see
Testing for formaldehyde is the only
way to know the concentration in a
given home. Building codes and green
certification programs currently focus
primarily on energy and resource con-
servation, to the detriment of occupants’
health. The skills of the industrial hy-
gienist are necessary to adequately ad-
dress indoor air quality concerns. The
time has come to bring those skills into
the residential setting.
Bud Offermann, PE, CIH, is president of Indoor Envi-ronmentalEngineering,aSanFrancisco-basedIAQ
state-wide study of residential ventilation and IAQ in
Study of High Formaldehyde Exposures
in California Residences
BY BUD OFFERMANN
In 2005, my San Francisco-based IAQ research firm, Indoor
Environmental Engineering, conducted a multi-season study
of ventilation and indoor air quality in 108 new single-family
detached homes in California. Indoor and outdoor air concentrations of 22 volatile organic compounds, formaldehyde, acetaldehyde, PM2.5, nitrogen dioxide, carbon monoxide,
carbon dioxide, temperature, and relative humidity were
measured over 24-hour periods. The outdoor air ventilation
rates were determined concurrently with the air contaminant
measurements using tracer gas measurements.
Formaldehyde concentrations were measured according to
ASTM Standard D5197-03 by drawing air at a constant rate
with a pump through a solid sorbent cartridge (i.e., silica gel
impregnated with dinitrophenylhydrazine, DNPH).
The occupants in approximately one-third of the homes did
not use their windows during the 24-hour test day, and occupants in 15 percent of the homes did not use their windows
during the entire preceding week. The median 24-hour measurement for air exchange rates was 0.26 ACH, with a range of
0.09 ACH to 5. 3 ACH. A total of 67 percent of the homes had
outdoor air exchange rates below the 2006 California Building
Code requirement of 0.35 ACH.
The only indoor air contaminants that exceeded recommended non-cancer and non-reproductive toxicity guidelines
were formaldehyde and PM2.5. Almost all homes (98 percent)
exceeded California’s 2008 Chronic and 8-hour Reference
Exposure Levels for irritant effects of 7. 3 ppb; 59 percent
exceeded the 2005 California Air Resources Board’s indoor
air guideline for irritant effects of 27 ppb; and 28 percent exceeded the 2008 Acute Reference Exposure Levels for irritant effects of 45 ppb. For PM2.5, only one home, with an
indoor concentration of 36 µg/m3, exceeded the U.S. Environmental Protection Agency’s PM2.5 24-hour ambient air
quality standard of 35 µg/m3.
The percentages of homes exceeding the No Significant
Risk Levels for cancer were 100 percent for formaldehyde
and 93 percent for acetaldehyde. The percentage of homes
exceeding the No Significant Risk Levels concentration for
five other volatile organic compounds ranged from 8 percent
for trichloromethane (chloroform) and tetrachloroethene to 63
percent for benzene.
For the two volatile organic compounds with Maximum Allowable Dose Levels for reproductive toxicity, only the benzene Maximum Allowable Dose Levels was exceeded. A total
of 20 percent of the homes had indoor benzene concentrations that exceeded the calculated indoor Maximum Allowable Dose Levels concentration.
The primary source of the indoor concentrations of
formaldehyde and acetaldehyde, which were the two air contaminants that most frequently exceeded recommended
guidelines, is believed to be composite wood products.
For both formaldehyde and acetaldehyde concentrations,
the outdoor air exchange rate was determined to have a significant inverse correlation. For formaldehyde concentrations,
indoor air temperature was determined to have a significant
positive correlation. These results indicate that as outdoor air
exchange rates decrease or the indoor temperate increases,
indoor concentrations of formaldehyde increase.
The following are the conclusions from this study:
• Many homeowners never open their windows or doors, especially during the winter months.
• New homes in California are built relatively tight: natural air
infiltration rates through the building envelope can be very
low (e.g., 0.1 ACH).
• In new homes with low outdoor air exchange rates, indoor
concentrations of air contaminants with indoor sources,
such as formaldehyde and some other volatile organic
compounds, can become substantially elevated and exceed recommended exposure guidelines.
• Ducted outdoor air mechanical outdoor air ventilation systems generally did not perform well as a result of the low
outdoor airflow rates and short operating times. A total of
64 percent of ducted outdoor air systems failed to meet the
American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 62.2-2007 standard for residential ventilation, which is referenced in the California
Energy Commission’s 2008 Building Energy Efficiency
• Heat recovery ventilator mechanical outdoor air ventilation
systems performed much better than ducted outdoor air
systems. All of the heat recovery ventilator systems met
the California Energy Commission’s new 2008 Building
Energy Efficiency Standards.