Pregnant women who live near hazardous waste sites have an increased
risk of bearing children with major birth defects, a new study has
Researchers at the Yale University School of Medicine and the New York
State Department of Health (NYDOH) studied 27,115 births and concluded
that, overall, women living within a mile of an inactive dump have a
12% greater chance of bearing a child with a major birth defect,
compared to women living further than a mile from a dump.
The researchers looked at 590 inactive dump sites in 20 northern New
York Counties. Among the 590 sites studied, 90 were ranked as "high
risk" sites because there was documented evidence that chemicals had
migrated off the sites. The study found that women living within a mile
of any of these 90 sites had a 63% greater chance of bearing a child
with a major birth defect, compared to women living further than a mile
from all of the 90 sites.
The study posed four questions: first, is residential proximity
(closeness) to dumps associated with major birth defects? Second, are
particular types of birth defects associated with proximity to dumps?
Third, do particular characteristics of dumps (for example, documented
off-site migration of chemicals) increase a waste site's risk to
neighbors' health? Fourth, are specific chemical groups (such as
pesticides or metals) associated with particular birth defects as
previous studies have shown (for example, pesticides and cleft palate)?
The answers to all four questions turned out to be yes.
The Yale/NYDOH study began by examining the New York State Congenital
Malformation Registry; they found records of 9,313 infants born in 20
northern New York counties during the two-year period 1983-1984 with
major birth defects of the nervous system, muscle and skeletal system,
and skin. They omitted New York City.
The researchers then selected 17,802 normal infants from the same 20
counties born during the same time-period, to serve as controls.
The residential locations of the mothers of all 27,115 infants were
then converted into latitude and longitude, so they could be plotted on
a map, and the distance to the nearest dump was calculated for each
residence. (Residential location was determined to be accurate within
200 feet in 80% of the cases, and within 1300 feet in the remaining 20
percent of cases.) Then a comparison was made between the infants born
to women who lived within a mile of a dump, versus infants born to
women who lived more than a mile from any dump. Infants whose mothers
lived a mile or less from a dump had a 12 percent greater chance of
being born with a major birth defect.
During the second part of the study, each of the 590 dumps was assigned
a numerical hazard score, based on criteria developed by EPA [U.S.
Environmental Protection Agency] and modified by NYDOH. Dumps
considered most likely to produce toxic exposures of any kind (through
breathing, ingestion, or skin contact, via air, water, or soil)
received the highest scores. Then each individual woman in the study
was assigned an "exposure risk"--a number that combined her proximity
to a dump with the hazard score for that dump. Then the women were
split into two groups--those with a "high exposure risk" (greater than
30) and those with a "low exposure risk" (less than 30).
Further analysis revealed that specific kinds of birth defects are
associated with proximity to dumps, particularly birth defects of the
nervous system (29 percent more likely), musculoskeletal system (16
percent more likely), and the skin (also known as the body's integument
system) (32 percent more likely). Birth defects of the digestive system
and oral clefts were not significantly associated with proximity to
The danger of birth defects is especially high near dumps where off-
site migration of wastes has been documented. Near the 90 dumps with
documented off-site migration, birth defects are 63% more likely to
occur, compared to dumps where off-site migration has not been
Lastly, the study revealed that dumps containing specific kinds of
toxins were associated with specific kinds of birth defects, thus
confirming associations that have been noted in previous studies. For
example, pesticides were associated with cleft palate in the Yale/NYDOH
study. Pesticides and birth defects of the muscular system were also
associated. Metals and solvents were each associated with nervous
system birth defects. Plastics were associated with chromosome
Strengths of this study
Previous studies have found a connection between a mother's exposure to
chemicals and birth defects in her offspring, but the Yale/NYDOH
study is the first to examine such a large number of births, and thus
is far more convincing than previous studies. This study also did not
rely upon information provided by individuals about themselves, so
"recall bias" (errors or distortions caused by faulty memory) was
eliminated from this study. A previous study of residents near the
Stringfellow Acid Pits had shown that people near the Stringfellow dump
reported excessive occurrences of ear infections, bronchitis, asthma,
angina pectoris [heart-related chest pains], skin rashes, blurred
vision, pain in the ears, daily cough for more than a month, nausea,
frequent diarrhea, unsteady gait when walking, and frequent urination.
However, the Stringfellow researchers were unable to rule out the
effects of "recall bias" because they relied entirely on people telling
them about their symptoms, so skeptics remained unconvinced that the
study revealed anything about real diseases caused by the nearby dump.
As the authors of the Yale/NYDOH study said, their results in this
study do not prove a cause-and-effect relationship between birth
defects and proximity to dumps, but their results "do exhibit many
characteristics of causal associations." Each of the four types of
analysis (the four questions discussed previously) showed increased
rates of birth defects associated with proximity to dumps. As the
analysis became more specific, the associations between dumps and
disease remained similar or became even stronger. Rates for certain
birth defects associated with chemical exposures in previous scientific
studies were statistically elevated, while other defects, with little
or no previous data to suggest a relationship with chemical exposure,
showed no increases. Finally, a kind of dose-response relationship was
apparent between proximity to higher-risk dumps and birth defects. In
other words, the closer a woman lived to a high-risk dump, the greater
were her chances of bearing a child with a major birth defect.
Limitations of this study
This study may underestimate the number of defective births associated
with proximity to dumps for two reasons: The study did not examine
spontaneous abortions and fetal deaths--both of which are known to be
associated with human exposures to chemicals. Furthermore, there is
evidence that about 20 percent of women move their residence during
pregnancy. If this were true, it would result in misclassification of
subjects, which would weaken the ability of the Yale/NYDOH study to
discern the full effect of living near dumps.
Lastly, the Yale/NYDOH study does not prove conclusively that chemicals
in the dumps CAUSED the birth defects because no actual chemical
exposures of women were measured. Proximity to dumps was used as a
surrogate (substitute) for exposure to chemicals. Since no chemical
exposures were actually measured, chemicals cannot be definitely
fingered as the cause of the birth defects. Furthermore the Yale/NYDOH
study did not take into account possible differences in lifestyle (for
example, tobacco and alcohol use), occupational exposures to chemicals,
and possible exposures to chemicals from nearby industrial operations.
Thus the Yale/NYDOH study is "highly suggestive" but is not sufficient,
by itself, to prove cause and effect.
Further studies are now underway to try to remedy the shortcomings of
the Yale/NYDOH study. Unfortunately, it will be several years, perhaps
a decade, before results of these follow-up studies will be published.
In the meantime, does the Yale/NYDOH study give us reason to be
concerned about pregnant women living within a mile of a dump? In our
opinion, definitely yes. We believe any pregnant woman who can avoid
living within a mile of a dump would be well-advised to do so. The
further away from industrial poisons, the better.
The authors of the Yale/NYDOH study said their study revealed a "small
additional risk" of bearing a child with a major birth defect. To them,
a 12 percent increase is "small." But look at it this way: the authors
say the "normal" occurrence of major birth defects in the 20 counties
they studied in New York is 30 defects per 1000 live births. Among
women living within a mile of a dump, the occurrence is 34 defects per
1000 live births--a 12 percent increase. In the period they studied,
1983-1984, there were 506,183 live births in the 20 counties. If NONE
of these women lived within a mile of a dump, the number of spontaneous
birth defects would be 15,186. On the other hand, if ALL the women
lived within a mile of a dump, there would be 17,210 babies with major
birth defects born during the 2-year period, or 17,210-15,186=2024
excess (dump-related) birth defects in a two- year period in the 20-
county area, or about 1000 excess (dump- related) major birth defects
each year in the 20-county area.
Would 1000 excess (dump-related) major birth defects each year in a 20-
county area be a "small" increase? DURING ONE PERSON'S LIFETIME, THERE
WOULD BE 70,000 ADDITIONAL (DUMP-RELATED) MAJOR BIRTH DEFECTS IN THE
20-COUNTY AREA. Viewed this way, it becomes hard to understand how the
New York Department of Health can call a 12-percent increase in major
birth defects "small." Furthermore, from the viewpoint of any one of
the mothers involved, such an increase no doubt seems frighteningly
 Sandra A. Geschwind and others, "Risk of Congenital Malformations
Associated With Proximity to Hazardous Waste Sites," AMERICAN JOURNAL
OF EPIDEMIOLOGY, Vol. 135 (1992), pgs. 1197-1207.
 For discussion of additional studies, see Anthony B. Miller and
others, ENVIRONMENTAL EPIDEMIOLOGY; PUBLIC HEALTH AND HAZARDOUS WASTES
(Washington, D.C.: National Academy Press, 1991).
 Dean B. Baker and others, "A Health Study of Two Communites [sic]
Near the Stringfellow Waste Disposal Site," ARCHIVES OF ENVIRONMENTAL
HEALTH Vol. 43 (Sept./Oct., 1988), pgs. 325-334.
Descriptor terms: health; birth defects; ny; landfilling; pesticides;
heavy metals; congenital malformations; congenital birth defects;
reproductive hazards; stringfellow acid pits; death; death statistics;