United States
Environmental Protection
Agency
Health Effects Research
Laboratory
Research Triangle Park NC 27711
 Research and Development
EPA-600/S1-81-057  Sept. 1981
 Project Summary
 Association  Between  Birth
 Defects and  Exposure  to
 Ambient  Vinyl  Chloride

 Gilles P. Theriault, Hilda Iturra, and Suzanne Gingras
  To better define the association
between exposure to vinyl chloride
monomer (VCM) and the occurrence
of birth defects, this epidemiological
study was made  in   Shawinigan,
Quebec, Canada, where a vinyl chloride
polymerization  plant  has operated
since 1943. Birth-defect rates in
Shawinigan during the  last 15 years
were compared with rates in three
other communities, and seasonal and
spatial variations in Shawinigan's
birth-defect rate were correlated with
estimated VCM concentrations in the
environment.

  Shawinigan had an excess of birth
defects which fluctuated seasonally in
a  way that  could correspond to
changes in VCM concentration in the
environment. Mothers who gave birth
to malformed children were younger
on average in Shawinigan than in the
comparison communities.  However,
there was  no excess of stillbirths in
Shawinigan, the excess in birth defects
involved most systems, and variation
in  birth-defect rates among school
districts could not be accounted for by
estimates of VCM in the atmosphere.
  The occupational and residential
histories of parents who gave birth to
malformed infants  were compared
with those of  parents of normal
infants. The two groups did not differ
in occupational exposure or closeness
of residence  to the vinyl chloride
polymerization plant.
  This Project Summary was devel-
oped by EPA's Health Effects Research
Laboratory, Research Triangle Park,
NC, to announce key findings of the
research report that is fully docu-
mented in a  separate report of the
same title (see Project Report ordering
information at back).


Introduction
  Vinyl chloride monomer (VCM) is
carcinogenic in man and other animals
and mutagenic in microbial assays,
Drosophila, yeast, mammalian cells,
and man. VCM generates  mutations
primarily through one of its metabolites,
chloroethylene oxide, and with the
involvement  of  liver  microsomal
enzymes. Although miscarriages and
fetal losses among the wives of workers
exposed to VCM  have been studied,
such effects remain  undocumented.
VCM was  found  in the  fetal and
maternal blood and the amniotic fluid of
pregnant rats after exposure  to air
containing VCM; two studies of VCM
teratogenicity  in animals failed  to
demonstrate fetal  malformations, but
showed increased fetal death rates.
  At normal temperature and pressure,
VCM is a gas; it liquifies at -13° C. It is
processed into polyvinyl chloride (PVC; a
plastic) through polymerization reac-
tions in autoclaves. The gas is released
into the environment during unloading,
processing, and autoclave-cleaning
operations. The concentration of VCM

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to which people in the community are
exposed  depends on  production rate,
wind direction, wind velocity, and
distance from the plant.
  In Shawinigan (population 27,000), a
vinyl chloride polymerization plant
(owned by B.F. Goodrich Co., Ltd.) has
operated since 1943 and currently
produces 25,000 tons/yr of PVC. Ten
cases of angiosarcoma of the liver have
been reported among workers at this
plant. In addition  to  the PVC plant,
Shawinigan  has two  chemical plants,
one  aluminum electrolysis plant, one
carbide plant, and one pulp and paper
mill. A great number of pollutants are
discharged  into  its environment. Fur-
thermore, prevailing winds tend to blow
from the  pollution sources towards the
town's residential areas.
  In 1975, a  high birth-defect incidence
(mostly central  nervous system abnor-
malities) was found in three Ohio towns
with PVC plants. However, two sub-
sequent studies failed  to find any
association between birth defects and
either work at or proximity of residence
to these plants. In a 1977 study, a higher
birth-defect rate was found in Shawinigan
than in Drummondville (a town without
a  PVC plant); the highest rates in
Shawinigan  were in the vicinity of the
plant. The present study was an attempt
to associate this high frequency of birth
defects with exposure  to VCM.
  One objective of this study  was to
establish birth-defect and stillbirth rates
in Shawinigan and to compare these
rates with those for other communities,
in an attempt to confirm the high birth-
defect rates previously observed. An-
other objective was to try to correlate
seasonal and  spatial  variations in the
birth-defect rate with variations in VCM
concentration in the environment. The
final objective  was to compare a group
of parents who gave birth to malformed
infants with  a  control  group of parents
of normal  children  with respect to
residential and occupational history and
several birth-defect risk factors.
  In determining birth-defect rates in
Shawinigan, the study  included  all
stillbirths and malformed children born
of mothers who resided within the city
limits of Shawinigan  at the time of
delivery  and who  delivered between
January  1,  1966,  and December 31,
1979. The  case-control study was
limited to a shorter  period (January
1973 to December 31,1979), because it
required information based  on the
mothers' recollection  of events  during
their pregnancies.  A  birth defect was
defined as a gross physical or anatomic
developmental anomaly present at birth
or detected at the hospital during the
first days after delivery.
  To assess  the importance of the
excess of birth defects in Shawinigan,
three comparison communities were
chosen, based on their similarity to
Shawinigan  in  population size  and
structure, socioeconomic  level,  and
medical-care  facilities. To take  into
account the influence of environmental
pollution, one town with an aluminum
plant but no VCM-emitting plant (Baie-
Comeau—Hauterive)  and two towns
with neither a VCM nor an aluminum
plant (Drummondville and Rimouski)
were chosen as control communities.
  The  Quebec Population Registry
provided the annual numbers  of births
and stillbirths  in the communities; as
the 1979 data  were not available,
numbers were estimated from the three
preceding years. Birth-defect  children
and controls were identified and data
were  collected from  several  medical
files and hospital rosters (delivery-room
daybooks, birth-defect rosters, discharge
lists, mothers' and children's medical
files, and birth rosters). Shawinigan's
14 school districts were used as the unit
of spatial distribution  of birth defects.
For the case-control study, the mothers
of affected infants and matched controls
were interviewed at home. Cases and
controls were matched by maternal age
within two years, sex of the infant, and
place of residence of the mother.
  Two  studies  were conducted to
assess vinyl chloride  concentration in
the air in Shawinigan. The first was a
study of the  feasibility of  measuring
VCM in the air at several locations in
Shawinigan using air  sampling  and
analysis techniques (summarized in an
appendix to the  report of the present
study).  Its conclusion was that environ-
mental VCM  concentrations could be
assessed by ambient  air sampling at
various sites in Shawinigan; depending
on location, sampling detected  levels up
to 45 ppb. During winter, VCM tended to
accumulate in the snow in the vicinity of
the plant,  and VCM concentrations
differed between indoor and outdoor
samples. The  report  recommended a
continuous one-year sampling program
with special attention to meteorologic,
topographic, and  demographic data to
establish the true VCM concentrations
to which the Shawinigan population is
exposed.
  Considering the high  cost of such a
sampling program, it was decided that
for  the present study, ambient vinyl \
chloride concentrations in Shawinigan
would be estimated using a dispersion
model based on production records and
the results of previous air-monitoring
activities. This study was conducted by a
subcontractor.  The dispersion  model
used the Pasquill-Gifford equation, and
its variables included wind direction and
velocity, rainfall, humidity,  tempera-
ture, topography, and estimated VCM
production and emissions. The  model
allowed construction of isopleths of
estimated vinyl chloride concentration
over Shawinigan.

Results
  From January 1966 through Decem-
ber 1979, there were 4534 live births
and 33 stillbirths in Shawinigan. Of the
live infants, 150 had birth defects, and
of the stillbirths, 9 had birth defects. The
birth defects  reported most frequently
were those  of the  musculoskeletal
system, followed by the cardiovascular,
central  nervous,  and urogenital sys-
tems. The ages of the mothers did not
differ significantly among the various
types of birth  defect.  Defects of the
central nervous  system (CNS)  were
particularly frequent among malformed
infants with short gestation  periods.    '
  The  yearly numbers of malformed
children per 100 births varied from 1.68
(in  1969)  to  6.84 (in 1973), with an
overall rate of 3.48. Detailed analysis of
the monthly distribution of birth defects
and the distribution by affected system
for  the year  1973 showed  no  single
large increase that could account for the
high rate in that year. Nor did the yearly
distribution by  system  show any par-
ticular feature that could account for the
annual  variation  in the overall rates.
Furthermore, birth-defect rates did not
consistently  increase or decrease with
time.
  The observed number of malformed
children in Shawiniganwashigherthan
would be expected based on the rate for
each comparison community or for all
three comparison communities together
(see Table 1). The excess birth defects in
Shawinigan  occurred  in the central
nervous, cardiovascular,  urogenital,
and  musculoskeletal systems, the eye
and ear, and the chest. As the types of
defects found in excess in Shawinigan
were also the  most  common types o1
defects overall,  it can be concluded thai
birth defects  in general were in excess
in Shawinigan. The proportion of mat
formed infants was greater in Shawinigar
than in the comparison  communities ir

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Table 1 . Number of Malformed Children Observed in Shawinigan Compared with
Comparison Communities (1966-1979)"
Affected
System
Central nervous
Cardiovascular
Gastrointestinal
Urogenital
Musculoskeletal
Mouth and upper
airways
Eye and ear
Chest
Syndromes and
other defects
Total
Observed
in
Shawinigan
30
37
11
30
49
17
6
3
6
159
Expected
Based on
Drummondville
19.69*
19.69**
9.04
19.15*
36.71
6.92**
1.06**
0.53*
6.92
102.68**
Expected
Based on
Baie-Comeau —
Hauterive
18.18*
13.94**
9.70
13.94**
27.88**
13.33
1.82*
—
9.70
98.80**
Expected Numbers Based on Rates for the
Expected
Based on
Rimouski
15.33**
43.06
10.95
13.14**
40.14
13.14
—
0.73
10.95
124.08**
Expected
Based on All
Comparison
Communities
17.96*
24.29*
9.80
15.72**
34. 70*
10.82
1.02**
0.41*
8.98
107.36**
  "Ratio of Poisson variable to its expectation (36); * indicates p < 0.05;
  ** indicates p< 0.01.
 all years except  1969 and 1972 (see
 Table 2).
   The number of stillbirths differed only
• between Shawinigan and Drummond-
 ville, where  the  number of stillbirths
 was significantly higher. The proportion
 of malformed children among the still-
 born was higher in Shawinigan than in
 the  comparison communities. This is
 consistent with previous findings of an
 excess of birth defects in Shawinigan.
 Mothers who gave  birth to malformed
children were significantly younger in
Shawinigan than in the comparison
communities for all  malformations
combined  and for defects of the CNS,
mouth and upper airways, and eye and
ear.  Children  in Shawinigan did  not
differ from those in  the comparison
communities in mean gestational age at
birth, except in  the case  of chest
malformation, for which the sample size
was  very small.
  Figure 1 compares the monthly birth-
defect rates for Shawinigan with those
for Drummondville and Rimouski The
Shawinigan curve is V-shaped, with the
lowest rates in  the summer, whereas
the curve for the comparison communi-
ties is flatter. The seasonal variation in
birth-defect  rates was  statistically
significant for Shawinigan, but not for
the comparison  communities.
  The  spatial  distribution  of birth
defects in Shawinigan with respect to
the PVC plant  was  analyzed;  in no
 Table 2,    Distribution of Malformed Children for Each Year (1966-1979)
Year
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
Total
Shawinigan
16
13
8
6
15
6
6
18
8
15
13
14
11
10
159
Ratea
3.54
3.52
2.30
1.68
4.70
2.08
2.19
6.84
2.97
4.40
3.98
4.56
3.33
3.11
3.48
Comparison
Communities
31
33
24
27
24
30
34
44
43
51
36
50
52
47
526
Rates
1.82
1.96
1.51
1.78
1.66
2.05
2.43
3.17
2.81
3.10
2.20
2.76
2.88
2.69
2.35
SH/ Comparison
Communities*'
1.95*
1.80
1.52
0.94
2.83*
1.01
0.90
2.16*
1.06
1.42
1.81
1.65
1.16
1.16
1.48*
95% Confidence
Interval
(1.08, 3.52}
(0.96, 3.391
(0.69, 3.341
(0.41, 2.18)
(1.55. 5.1 7 j
10.53, 1.94)
(0.36. 2.20)
(1.28, 3.65)
(0.48. 2.33)
(0.81. 2.49)
(0.93, 3.51)
(0.93, 2.93)
(0.61, 2.20)
(0.60. 2.26)
(1.24. 1.75)
 "^Number of malformed children per 100 births.
 """' indicates p < 0.05.

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   3-
   2-
 co
    1-
                                        Shawinigan (1966-1979) •
                                        Drummondville and
                                        Rimouski (1971-1977)
       JAN FEB MAR APR MAY  JUN JUL AUG SEP OCT
                                 Month of Birth
Figure 1.   Monthly distribution of birth-defect rates.
                                                              \     \
                                                             NOV DEC
school district did the ratio of observed
to expected number of birth  defects
differ significantly from 1. The four
districts  with  the  highest rates are
located on the north-south axis passing
through the vinyl  chloride plant; the
district in which the plant is located had
abcut the  expected number of birth
defects. The yearly average concentra-
tion of vinyl chloride was estimated for
each school district, based on data from
a study entitled "Dispersion Patterns of
Vinyl Chloride Emitted by B.F. Goodrich
Co., Ltd.,  Shawinigan, Clue." (which is
appended to the report of  the  present
study). Birth-defect rates did not differ
between  school districts with high and
low VCM  exposure, either for  all birth
defects or for CNS defects (see Table 3).
Likewise,  school districts  adjacent to
the plant did not differ from the other
school districts  in numbers of birth
defects (total or CNS), nor  did  districts
differ within and  beyond  a one-mile
radius of the vinyl chloride plant.
  For the period  January 1973 to
December 1979,  68 cases of birth
defects were identified in  Shawinigan
and matched with controls (42 male and
26 female pairs). Five of the cases were
stillborn; all of the controls were  born
alive. There was no significant difference
between  cases and controls in number
of weeks' gestation at delivery.  The
frequencies of previous birth defects in
the families of cases and  controls did
                                        not differ significantly, nor was there a
                                        significant difference between case and
                                        control  mothers in number of previous
                                        pregnancies.
                                          Mothers of malformed infants reported
                                        no excess of diseases during pregnancy;
                                        however, the  following diseases sus-
                                        pected to bear a high risk of birth defect
                                        were reported more frequently by case
                                        than by control mothers: rubella,
                                        hydramnios,  epilepsy, nonpsychotic
                                        mental  disorders, and psychosis. There
                                        was no significant difference between
                                        case and control mothers in number of
                             previous  abortions.  There was one
                             pievious  stillbirth among  the  control
                             mothers and none for the case mothers;
                             there was one previous malformed child
                             in each of the two groups. There was no
                             significant  difference between cases
                             and controls  in the  father's age.  No
                             mother (case or control) was exposed to
                             X-rays during the first trimester of
                             pregnancy,  and  only  one case  mother
                             was exposed during the second  third of
                             pregnancy;  exposure  during  the third
                             trimester did not differ significantly
                             between case and control mothers.
                              Table 4 summarizes the  mothers'
                             occupations before and during their
                             pregnancies. None of  the women were
                             ever exposed to VCM  at work before or
                             during pregnancy. The working experi-
                             ences of the case and control mothers
                             before and during pregnancy  did not
                             differ, nor did their smoking  habits or
                             alcohol consumption. Two  mothers of
                             defective  infants reported having used
                             the drug LSD before their pregnancies.
                             There was no significant difference
                             between  cases  and  controls  in the
                             father's  occupational  exposure to
                             chemicals,  and  no fathers were ever
                             exposed to vinyl chloride (see Table 5).
                             The distance  between each  mother's
                             place  of residence and the VCM plant
                             was measured to ± 100 m,  using a map
                             of  the city; there was no significant
                             difference between the two groups in
                             distance from the VCM plant.
                                        Table 3.
                             Discussion
                               Some observations of this study
                             support the existence of an association
                             between VCM  in  the air and  birth
                             defects  in  the  exposed  community,

Comparison of Total Birth Defects* and CNS Birth Defects* Between
School  Districts  with High  and  Low Atmospheric Vinyl Chloride
Concentration
                                                                School Districts
                                     School Districts

Births with
defects
Births without
defects
Births with CNS
defects
Births without
CNS defects
Total births
With High VCM Levels*
87
2285
16
2356
2372
With Low VCM Levels
70
2125
13
2182
2195
Total
1'57
4410
29
4538
4567
                                         aX2i = 0.80; p> 0.35.
                                         t>X^^ =0.10; p> 0.70.
                                         "School districts nos. 1. 3, 5, 6,  7, and 8.

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Table 4.    Distribution of Cases and Controls by Mother's Occupation*

                                   Cases                   Control
Mother's Before
Occupation Pregnancy
Work outside home without
exposure to chemicals
Work in VCM industry
Work outside home with
exposure to chemicals
Stay at home
Total
41
0

2
25
68
During
Pregnancy
22
0

1
45
68
Before
Pregnancy
42
0

2
24
68
During
Pregnancy
20
0

1
47
68
 ^Partitioning stay at home vs. work outside home before pregnancy:
 X2,=0.03; p>0.85. Partitioning stay at home vs. work outside home during pregnancy:
 X2, =0.13;p>0.71.
while others tend to contradict such an
association. High birth-defect rates  in
Shawinigan were confirmed for a 15-
year period, and women who gave birth
to malformed children were, on average,
younger in Shawinigan than in the
comparison communities. These results
are consistent with previous findings for
three Ohio towns with PVC plants.
  The present  study revealed seasonal
variation in birth-defect rates that could
correspond to variation in atmospheric
VCM concentrations. VCM could not be
measured in air samples during Decem-
ber, January,  and February.  It  is
believed that during these months, VCM
tends to accumulate near the plant as a
liquid, because the outdoor temperature
is below its liquefaction point; this VCM
would be released into  the air in the
spring. Birth-defect rates were lowest in
September, which is eight months after
midwinter, corresponding  to the time
between the first third of pregnancy and
delivery. This observation would tend  to
support  an association between VCM
concentration in  the air and birth
defects  in  the community. One con-
sultant believed that below its liquefac-
tion point, VCM would remain in the air
in droplets, at a concentration similar to
that found at higher temperatures.
However,  because people spend  more
time indoors during the winter than the
rest of the year, winter exposure would
tend to be low in any case.
  On the other hand,  several observa-
tions of the present study tend to argue
against any association between  VCM
concentration in the air  and  birth
defects in the community. The spatial
distribution of birth defects in Shawinigan
cannot be explained  on  the basis of
estimates  of VCM concentrations in the
community. Malformation  rates  were
not relatively high either near the  plant
or in the area where VCM concentrations
were estimated to be  highest, and the
school district with  the  highest birth-
defect  rate was  far  from  the plant.
However, VCM concentrations were not
measured directly, but estimated by a
theoretical dispersion  model based on
approximate production  and emission
values, because the B.F. Goodrich Co.
would not release the  actual values.
Table 5.    Distribution of Cases and Controls by Father's Occupation*

   Father's Occupation                   Cases                   Controls

 Ever worked in vinyl
  chloride industry
 Ever worked in industries
  with exposure to chemicals
   0


  20
 0


25
Never worked in industries
with exposure to chemicals
Unknown
Total
43
5
68
39
4
68
 "X2! =0.73;p>0.39.
  There  was no difference in  occupa-
 tional or  residential history between the
 parents  who gave birth to malformed
 infants and the control parents.  Both
 groups resided at similar distances from
 the plant, and none of the parents had
 worked  at the  plant. Furthermore, all
 types of  birth defects were in excess in
 Shawinigan, rather than those of any
 particular system. These results agree
 with those  for the  three Ohio cities;
 however, agents known to be teratogenic
 in humans  and experimental  animals
 have very specific effects, and it seems
 unlikely  that any agent would  produce
 the variety of malformations found in
 excess in Shawinipan.
  Possible explanations of the results
 as artifactual are not convincing.  It is
 unlikely  that Shawinigan's physicians
 were'more  inclined  to diagnose birth
 defects than were  physicians  in the
 comparison communities. Birth defects
 were included in this study on the basis
 of their  obviousness,  and the birth-
 defect  rates were the same in the three
 comparison communities. Furthermore,
 for severe birth  defects like those of the
 CNS,  which cannot  be  misdiagnosed,
 rates were much higher in Shawinigan
 than in  any of the  comparison com-
 munities. The method by which the data
 were collected made it very unlikely that
 a bias  in  the quality of the information
 from  the archives  of the regional
 hospitals could have influenced the
 results.
  The possibility remains that pregnant
 mothers  residing outside of Shawinigan
 who were at risk of having a malformed
 child migrated to the city  for delivery,
 thereby increasing the birth-defect rate
 for that town. In the case-control study,
 six  mothers (6.7%) were rejected
 because  they had moved to the city of
 Shawinigan  after the  first third of
 pregnancy, and four  more cases were
 untraceable. Thus, as many as 11% of
 the birth-defect cases observed in
 Shawinigan  might actually have come
from elsewhere, reducing  the number
 of observed cases to  142.  However,
 birth-defect  rates would still  be  sig-
 nificantly higher than in the comparison
 communities, leading us to believe that
the  excess noted in  Shawinigan  was
 real.
  Animal studies  have shown that
exposure to  high levels of VCM during
pregnancy results more often  in high
rates of fetal loss and miscarriage than
 in birth defects. However, stillbirth rates
were no  higher in Shawinigan  than in
the comparison communities, and m the

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case-control study, abortion rates were
not higher for  case than for control
mothers.
  Several industries in  Shawinigan
emit pollutants into the  atmosphere,
and several of the pollutants may
interact to generate potent mutagenic
or teratogenic chemicals in  the com-
munity. The analysis of such an envi-
ronment and its association with the
excess of birth defects was beyond the
scope of the present study. However, in
the case-control study, there was  no
difference between the numbers of case
and control parents who worked at the
aluminum plant, and the comparison
community  with  an aluminum elec-
trolysis plant (Baie-Comeau—Hauterive)
had lower birth-defect rates than did
Shawinigan. Thus, the aluminum  in-
dustry probably was not solely respon-
sible for the excess of birth defects in
Shawinigan.
  Among risk factors (other than occu-
pational or environmental  exposure to a
pollutant) known to be associated with
birth  defects,  epilepsy  and mental
disorders before and during pregnancy
and the use of the  drug LSD before
pregnancy were  reported more fre-
quently by mothers  of malformed
children than by control mothers. Drugs
prescribed to control epilepsy have been
reported to  be associated with  birth
defects and could account for a few birth
defects observed  in Shawinigan,  as
could LSD.  No other risk factor was
reported more frequently by the case
than by the control mothers.
  An association between VCM in the
air  and birth defects in  the exposed
community cannot be substantiated at
the present time. If the association
exists,  it cannot be  measured by the
methods used in this and in  previous
studies  or in populations of  the sizes
studied  so far.

Conclusions
  The conclusions of this  study can be
summarized as  follows:
  1. For the years 1966 through 1979,
     there was an  excess  of birth
     defects in the population  of
     Shawinigan, Quebec. This result
     is  similar to the  findings for
     several U.S.  cities  where vinyl
     polymerization plants operate.
  2. Birth-defect rates underwent a
     seasonal variation that could cor-
     respond to variation in the con-
     centration  of VCM in ambient air.
  3. Mothers from Shawinigan who
     gave birth to malformed infants
     were younger than mothers from
     the comparison communities who
     also gave birth to  malformed
     infants.
  4. The excess malformations involved
     not only  the central nervous
     system,  but  almost all body sys-
     tems.
  5. No correlation was found between
     the spatial distribution of  birth
     defects in the town and estimates
     of VCM  concentrations in the air.
     (These estimates were  based  on
     approximate  data, since informa-
     tion on PVC  production and  VCM
     emissions  was not available.)
  6. Occupational exposure as a causal
     agent was  ruled out, because
     none of  the  parents in the study
     had ever worked at the VCM plant.
  7. Cases and controls did not differ in
     distance of  residence  from the
     plant.
  8. No excess of stillbirths was ob-
     served in Shawinigan, and abortion
     rates were no higher for mothers
     of malformed infants  than for
     mothers of normal infants.
  Some  observations of  this study
support an association between VCM in
the air and birth defects in the exposed
community, while others tend to  indi-
cate that no such association exists.  As
the present results are inconclusive, the
possibility that VCM generates  birth
defects in human communities requires
further consideration. This would best
be  accomplished  through  a program
during the  next five to  ten years  to
monitor VCM concentration in the  air
and birth  defects  in the  exposed
communities.
   Cities P. Theriault, Hilda Iturra, and Suzanne Gingras are with the Department of
     Social and Preventive Medicine, Faculty of Medicine,  Laval  University,
     Ste-Foy, Quebec, Canada G1K 7P4.
   Jeff Beaubier and Gregg Wilkinson are the EPA Project Officers (see below).
   The complete report, entitled "Association Between Birth Defects and Exposure
     to Ambient Vinyl Chloride," (Order No. PBS 1-238 883; Cost: $11.00, 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 Officers can be contacted at:
           Health Effects Research Laboratory
           U.S. Environmental  Protection Agency
           Research Triangle Park, NC 27711
                                                                          •h US GOVERNMENT PRINTING OFFICE, 1981 —757012 7327

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