PROTECT: Puerto Rico Testsite for Exploring Contamination Threats
Project 3: Phthalate Exposure and Molecular Epidemiologic
Markers of Preterm Birth among Women in Puerto Rico
Luis O. Rivera1, José F. Cordero2, David E. Catonwine1, Kelly K. Ferguson1, John D. Meeker1*
1University
of Michigan, Ann Arbor, MI, USA; 2Universidad de Puerto Rico, Recinto de Ciencias Medicas
Background
Project Specific Aims
The preterm birth rate in Puerto Rico — now approaching 20 percent of live births — far exceeds
the average rate in the United States, a discrepancy that is not explained by other socio-cultural
factors. Puerto Rico has a large number of “Superfund” sites — locations identified as high-risk for
the public by the Environmental Protection Agency — in addition to more than 150 potential
hazardous waste sites throughout the island. As part of an epidemiological study of pregnant
women in Puerto Rico, PROTECT researchers will follow a group through pregnancy, collect data
on their everyday activities, measure their potential exposure to chemicals and identify correlations
between exposure and subsequent risk for preterm birth. Based on the data, the PROTECT team
will develop environmentally sustainable ways to mitigate the effects of toxic contaminants that
exist in groundwater.
25.0
20.0
15.0
P
e
r
c
e
n
t
a
g
e
Puerto Rico
USA
10.0
5.0
0.0
1990
1992
1994
1996
1998
2000
2002
2004
Year
Project Title
Other
Research
Project Leader
Support Core
Pollutant activation of cell pathways in gestational Tissues
J. Meeker
3
Phthalate exposure and molecular epidemiologic markers of
preterm birth among women in Puerto Rico
Epidemiologist
I. Padilla
4
Dynamic transport and exposure pathways of contaminants in karst
groundwater systems
Hydrogeologic Engineer
A. Alshawabkeh
5
Green remediation by solar energy conversion into electrolysis in
groundwater
Geoenvironmental Engineer
Core A: Administrative Core
Core B: Research Translation
Core E: Training Core
R. Loch-Caruso
Toxicologist
Core D: Data Management and Modeling
Biochemist
Core C: Human Subjects and Sampling
2
Discovery of xenobiotics associated with preterm Birth
Methods
Cores
R. Giese
1
Specific Aim #1: Define the distribution of urinary phthalate metabolites in pregnant women in
Puerto Rico, and determine individual factors and activities associated with elevated phthalate
exposure among the women.
Specific Aim #2: Assess the relationship of maternal exposure to phthalates with gestation length
and preterm birth among women in Puerto Rico.
Specific Aim #3: Provide epidemiologic evidence for potential mechanistic pathways between
phthalate exposure and preterm birth and/or gestational age. Specifically, markers of 1) endocrine
disruption, 2) inflammation, and 3) oxidative stress/genotoxicity will be investigated.
Exploratory Aims: Identify polymorphic genotypes related to inter-individual variation in phthalate
metabolism, and explore evidence of individual susceptibility and gene-environment interactions
using specific polymorphisms involved in phthalate metabolism and hypothesized mechanistic
pathways in preterm birth.
Figure 2. Preterm birth rates, US & Puerto Rico, 1990 - 2005.
Figure 1. Superfund sites in Puerto Rico (13 are on the final NPL list)
Project No.
We are conducting a prospective cohort study among 900 pregnant women in Puerto Rico that will
utilize state-of-the-art methods for estimating phthalate exposure and for assessing molecular
epidemiologic markers to provide much needed human data on predictors of preterm birth in Puerto
Rico. The study also aims to identify conditions and activities contributing to high phthalate exposures
that can lead to effective exposure reduction strategies. In addition, our exploratory aims will provide
new information on phthalate metabolism and individual exposure susceptibility, data which is greatly
needed from human studies especially among pregnant women (NTP 2005), and information on the
interaction of phthalates with genetic markers of interest in preterm birth risk.
Table 1. Summary of Research Projects and Research Support Cores
Phthalates and Preterm Birth
Phthalates are a group of man-made chemicals widely used in a range of industrial applications.
High molecular weight phthalates (e.g. di(2-ethylhexyl) phthalate [DEHP]), are primarily used as
plasticizers in the manufacture of flexible vinyl plastic (e.g. PVC) which, in turn, is used in
consumer products, flooring and wall coverings, food contact applications, and medical devices
(ATSDR 2002; Hauser and Calafat 2005). DEHP concentrations in plastic products may be as high
as 40% by weight (CDC 2005). Low molecular weight phthalates (e.g. diethyl phthalate [DEP] and
dibutyl phthalate [DBP]) are used in personal-care products (e.g. perfumes, lotions, cosmetics), as
solvents and plasticizers for cellulose acetate, and in making lacquers, varnishes, and coatings,
including those used to provide timed releases in some pharmaceuticals. (ATSDR 2001;1995).
Subjects will include 900 Puerto Rican mother-infant pairs who are recruited through the
Human Subjects and Sampling Core (Core C). All subjects are recruited through participating
hospitals and physician's clinics in Puerto Rico.
Eligibility criteria: Our eligibility criteria included pregnant women who have not completed
20 weeks of gestation at the time of recruitment, have had a first trimester ultrasound to
estimate gestational age, are resident of the study area in Puerto Rico's northern coast, and
plan to deliver at a participating hospital.
Exclusion criteria: Women below the age of 18 or over 40 will be excluded, as will multiple
gestations and pregnancies stemming from assisted reproductive technologies (ART).
Initial Screening
Delivery
Potentially eligible women
identified at prenatal clinics
and participating hospitals
Women provided study
information
Consent
Cord blood and placental
sample collection
Data abstracted from Medical
Records
Follow-up data collected on
residence, occupation, medical
or pregnancy complications
Second Trimester (V1)
•Data on residence,
pregnancy history, current
pregnancy, etc.
In-Home Visit (V2)
Between ~20- and ~28-week visits
Residence location (GPS)
Data on medical, pregnancy,
occupational, residence, and exposure
history, lifestyle, diet, etc.
Tap water sample, house dust sample
Urine and blood sample collected
Product Use Form
•Urine and blood sample
collected
•Food Frequency
Questionnaire
•Data abstracted from
Medical Records
Third Trimester (V3)
~28 week clinic visit
Follow-up data collected on
residence, occupational,
medical changes
Urine and blood sample
collected
Product Use Form for Urine
Samples
Toe nails and hair collected
Data abstracted from Medical
Records
Figure 4. Recruitment and data/sample collection timeline for PROTECT Human Subjects Core
Phthalates are classified as emerging pollutants of concern to the SRP and are associated with
reduced gestational age and other effects potentially linked with preterm birth, including
inflammation, endocrine disruption, and oxidative stress.
Significance
In a small nested case-control pilot study conducted within an ongoing cohort study in Mexico, we
recently found that women who delivered preterm had significantly higher concentrations of urinary
phthalate metabolites compared to women who delivered at term (Meeker et al. 2009: Table 2).
There is a need to better characterize human exposure to and toxicological effects of phthalates and
other Superfund and related contaminants in order to understand their possible role in preterm birth.
This information can then be used to develop effective exposure reduction and prevention strategies.
Term
(n=30)
Preterm
(n=30)
Term (n=30)
Preterm (n=30)
pvalue
MBP
38.1
89.9
33.4 (21.3, 74.0)
97.1 (56.0, 139)
0.005
MCPP
1.1
2.4
1.3 (0.5, 2.0)
2.3 (1.1, 4.9)
0.002
MBzP
2.3
5.2
2.9 (1.0, 5.2)
5.4 (2.6, 9.5)
0.01
MEP
112
204
108 (47.1, 224)
171 (69.4, 437)
0.1
MEHP
2.3
3.7
3.0 (0.6, 4.4)
4.3 (2.2, 7.1)
0.06
MEHHP
13.6
24.0
17.1 (6.2, 28.4)
28.7 (18.1,
37.5)
0.04
20.8 (14.4,
25.5)
0.04
MEOHP
10.4
18.9
Acknowledgements
13.6 (5.0, 24.5)
5.3
6.0
Urine MEHP (ng/ml)
Geometric Mean
Phthalate
Metabolite
Median (25th, 75th percentile)
5.0
4.0
2.7
29.7
51.2
38.2 (14.3, 53.8)
55.2 (39.2,
73.3)
0.02
Sum DEHP
metabolites
57.8
99.3
71.5 (26.8, 113)
112 (69.8, 135)
0.03
Table 2. Higher Phthalate Metabolites in Preterm Birth Cases vs.
Controls: Geometric mean & median 3rd trimester urinary phthalate
metabolite concentrations in women with term or preterm births.
References
3.0
2.3
2.3
2.0
1.0
Preterm
0.0
MECPP
This program is supported by Award Number P42ES017198 from the National Institute of
Environmental Health Sciences.
*Address correspondence to: John D. Meeker, Department of Environmental Health Sciences
Telephone: (734) 764-7184 Fax: (734) 936-7283. Email: meekerj@umich.edu
Term
Low MEHP%
High MEHP%
Figure 3. Evidence for Interaction and Individual Susceptibility:
Geometric mean MEHP concentrations (ng/ml) in women delivering
term or preterm when stratified by MEHP% (< or > median).
Difference in MEHP between term and preterm births was
statistically significant among women with high MEHP% (p=0.03).
•ATSDR. 1995 Toxicological Profile for Diethyl phthalate (DEP). Atlanta, GA: Agency for Toxic Substances and Disease
Registry.
•ATSDR. 2001 Toxicological Profile for Di-n-butyl phthalate (DBP). Atlanta, GA: Agency for Toxic Substances and Disease
Registry.
•ATSDR. 2002 Toxicological Profile for Di(2-ethylhexyl)phthalate (DEHP). Atlanta, GA: Agency for Toxic Substances and
Disease Registry.
•CDC. 2005 Third National Report on Human Exposure to Environmental Chemicals. Washington, DC: Centers for Disease
Control and Prevention.
•Hauser R, Calafat AM. 2005. Phthalates and human health. Occup Environ Med 62:806-818.
•Meeker JD, Hu H, Cantonwine DE, et al. Urinary phthalate metabolites in relation to preterm birth in Mexico City. Environ
Health Perspect 117:1587-1592.
•NTP. 2005 NTP-CERHR Expert panel update on the reproductive and developmental toxicity of Di(2-ethylhexyl) phthalate.
Research Triangle Park, NC: Center for the Evaluation of Risks to Human Reproduction, National Toxicology Program, U.S.
Department of Health and Human Services.
www.neu.edu/protect