United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Las Vegas, NV 89193-3478
Research and Development
EPA/600/S4-91/006 Mar. 1992
Project Summary
Time Spent in Activities,
Locations, and
Microenvironments:
A California National
Comparison
John P. Robinson and Jacob Thomas
This report reviews data on the meth-
odological background and results from
the 1987-88 California Air Resources
Board (GARB) time activity study and
from a similar 1985 national study of
Americans' Use of Time, conducted at
the University of Maryland, College
Park. To facilitate comparisons, data
from the national study were receded
to be as comparable as possible to the
CARB code categories. For the same
reason, these initial comparative analy-
ses were restricted to the age 18-64
working population in the two samples.
As a result, the data on average dis-
tributions of time in activities compared
favorably across the two samples. Cali-
fornians tended to report more average
time at work and commuting to work in
the diaries than was true nationally.
They also reported less average time
doing housework and caring for chil-
dren than was found nationally. Time
spent shopping in the CARB study was
slightly higher. In general, the differ-
ences in family care activities were
greater among women than among men
across the two samples. CARB respon-
dents also reported more time sleeping
and eating meals away from home, less
time eating meals at home, less time
grooming and less time on non-ascer-
tained activities.
Californians reported more time spent
at fairs and other entertainment events,
and more time reading than was true in
the national sample, and these differ-
ences were also more pronounced
among women in the two samples. Cali-
fornia women reported less time doing
domestic craft activities and in conver-
sation. At the same time, Californians
reported more time spent traveling, and
these differences were found mainly
among men.
Despite these differences, the two
data sets showed a remarkable similar-
ity in patterns of activity. That was less
true for the location codes, however.
Several sources of discrepancy were
found in the comparison of these data,
including time spent in automobiles vs.
other modes of transit. A receding of
the location data from the national
study provided some resolution of the
differences that were found, but sev-
eral differences remained—particularly
the greater amounts of time spent at
home and in the yard in the national
sample.
The strong similarities of the aver-
age time for the activity data indicate
that the California data could be used
to generate a better set of location
codings for the national data. This is
particularly true for estimates of out-
door time spent doing paid work, which
was not differentiated in the 1985 na-
tional data. It also means that the
supplemental CARB data on specific
exposure (e.g., passive cigarette smoke,
gasoline and service station visitations)
may have national implications. Never-
theless, a separate national study that
could build and expand upon the de-
velopmental work initiated in the CARB
study and oriented to exposure assess-
ment is needed.
This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings of the research
Printed on Recycled Paper
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project that is fully documented In a
separate report of the same tttl& (see
Project Report ordering information
below).
A major reason for analyzing time-diary
data is to estimate time spent in various
microenvironments. Microenvironments
refer neither solely to activities nor solely
to locations but to the combination of ac-
tivities and locations that yield similar con-
centrations or potential exposures. For this
report, 16 separate microenvironments
. (combinations of location and activity) were
defined for the purpose of comparing the
estimates from the U.S. national and GARB
studies. These were based on a collaps-
ing of the original 34 and 44 location codes
-to 10 and the activity codes from 90+ to
10. This revised list of locations includes
residences (both indoor and outdoor), work
locations, restaurants and bars, travel
modes, and places automobiles are
parked, serviced, and maintained.
Similiarly, activity distinctions include fam-
ily care, shopping, work/study, recreation
and travel. Known sources of carbon mon-
oxide, benzene, and other VOC's also
were reflected in our classifications.
In the final comparative analyses by
microenvironments, total samples—includ-
ing adolescents aged 12-17 and senior
citizens 'aged 65 _and over in "both the
GARB study and in the maiiback portion
of the national study-^were used. The na-
tional sample was weighted to provide a
ratio of 46.5"males to 53.5 females, in
equal proportion for each day of the week,
and for each quarter of the year. The time
weights provided for the GARB study
(which adjusts for strata as well as week-
day and season) were used in weighting
them, in these analyses, .the average du-
ration spent by "doers" (the population
who reported spending time in the micro-
environment) in the two studies and the
proportion of "doers" are compared.
Notable differences were found in the
estimates from the national and California
data for the microenvironment codes cre-
ated for this report. These resulted mainly
from differences in the location coding
schemes used in the two studies. Many of
these gaps were closed by the recoding
of selected location codes in the national
study, but that exercise also produced
some new divergences. Most notably,
these recocted data suggest that Califor-
nians spend most of their outdoor time in
away-from-home settings in contrast to
the greater time spent in yards and other
at-home outdoor environments In the na-
tional study. Although this would be con-
sistent with an image of more cramped
outdoor living environments in California
{or of more attractive outdoor environments
away from home), this result needs confir-
mation from independent data sources.
Many of the location coding differences,
therefore, seem to account for the differ-
ences in microenvironments. This includes
the greater times reported in California
inside garages (autoplaces), restaurants/
bars, and motor vehicles. It also includes
the longer time spent doing physical ac-
tivities in outdoor locations and travel by
other transit modes mainly done outdoor
in the form of walking or waiting for buses.
On the other hand, we find Galifornians
reporting less time in such microenviron-
ments as work/school locations, kitchens,
and family care settings for house chores,
child care and shopping activities.
Nonetheless, some of the differences in
microenvironments that occur appear to
be related to location coding differences
in the two studies rather than to actual
differences in activity patterns. Indeed, the
relation of microenvironmenta! time and
gender, age, and type of day were re-
markably similar in the two data sets, indi-
cating that they do tap the same basic
elements of time expenditure.
John P. Robinson is with the Survey Research Center at the University of Maryland,
• College Park, MD 20742, and Jacob Thomas is with the General Sciences
Corporation, Laurel, MD 20707.
Joseph V. Behar Is the EPA Project Officer (see below).
The complete report, entitled "Time Spent in Activities, Locations, and Microenviron-
ments: A California National Comparison," (Order No. PB92-140789AS;
Cost: $19.00, subject to change) will be available only from:
National Technical Information Service .
5285 Port Royal Road
Springfield, VA 22161 . .
• Telephone: 703-487-4650 • . -
The EPA Project Officer can be contacted at:
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Las Vegas, NV 89193-3478
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
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