December 17, 2013. Marta Wegorzewska, PhD candidate, in collaboration with Dr. Seth Bokser, MD.
There was a time you lived in your mother’s uterus. You do not remember it, but it was a memorable time.
Often, that time is nine months long. The nine-month period ensures the fetus is developmentally ready for a new stage in life—babyhood. Babyhood requires lungs that breathe, a stomach that digests milk and an immune system that fights bugs. Until birth, the mother performs these tasks for the fetus.
Some fetuses transition into babyhood before they are prepared for this new stage in life. These babies are called premature babies or preemies. Scientists learned pregnant women who give birth to preemies are more likely to have been exposed to environmental contaminants called phthalates.1
Phthalates are chemicals added to plastics (shower curtains, rainwear, toys etc)2 to help soften them. Phthalates are also added to personal-care products including soap, shampoo, lotion and deodorant.3 Most people, including pregnant women, unintentionally encounter phthalates regularly in their environment.
Over time, phthalates leak out of plastics and contaminate the food and water we ingest.4 People can also come into contact with phthalates when they apply products containing the chemicals onto their skin.3
A recent case-control study1 identified a correlation between exposure to phthalates during pregnancy and premature delivery of the baby. It showed women who went into labor too early had higher levels of phthalates in their urine.1 This was the largest study done on phthalates and premature birth to date. This study does not prove phthalates cause babies to be born too early, but it provides reason for scientists to study causation in the future.
Preterm labor occurs when babies are born before 37 weeks of gestation.5 It is a major problem worldwide, and the greatest contributor to neonatal morbidity and mortality.6 Babies born too early have problems breathing, eating and fighting infections due to underdeveloped lungs, intestines and immune systems, respectively.6
The current thought on why labor happens too soon is that inflammation in the uterine environment triggers the production of prostaglandins.5,7 Prostaglandins are hormones that start labor.7 Because phthalates are also linked to inflammation8 scientists wonder if phthalates can trigger prostaglandin production and early delivery.
There is no evidence at this time implicating phthalates as a cause for preterm labor. But there is also no benefit to being exposed to phthalates. If you chose to limit your exposure to phthalates, here are a few things you can do:
1. Read labels. Phthalate is a general term for a class of chemicals included in plastics and personal-care products. Look for the following chemical names and/or abbreviations:
DEHP (di-2-ethylhexyl phthalate)
MECPP (mono-(2-ehtyl-5-carboxypentyl) phthalate)
MEHP (mono-(2-ehtyl)-hexyl phthalate)
MBP (mono-n-butyl phthalate)
MEOHP (mono-(2-ethyl-5-oxohexyl) phthalate)
MCPP (mono-(3-carboxypropyl) phthalate)
2. Know your plastics. Choose plastics with the recycling code 1, 2 or 5. Recycling codes 3 and 7 are more likely to contain phthalates.
3. Avoid plastic and heat. Switch to glass when heating your food in the microwave. Avoid covering your food with plastic wrap. Use paper towels instead.
4. Check whether your personal care products contain phthalates.
This work is funded in part by the Graduate Student Internships for Career Exploration (GSICE) program at UCSF
This post was checked by the following science articles:
1) Ferguson KK, McElrath TF, Meeker JD. 2013. Environmental Phthalate Exposure and Preterm Birth. JAMA Pediatr. Online.
2) Fromme H, Gruber L, Schlummer M, Wolz G, Böhmer S, Angerer J, Mayer R, Liebl B, Bolte G. 2007. Intake of phthalates and di(2-ethylhexyl)-adipate: Results of the Integrated Exposure Assessment Survey based on duplicate diet samples and biomonitoring data. Environ. Int 33: 1012–1020
3) ATSDR. Toxicological profile for diethylphthalate, U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, Atlanta, GA, 1995.
4) ATSDR. Toxicological profile for di(2-ethylhexyl)phthalate (DEHP), U.S. Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, Atlanta, GA, 2002.
5) Goldenberg RL, Culhane JF, Iams JD, Romero R. 2008. Epidemiology and causes of preterm birth. Lancet 371:75-84.
6) McCormick MC. 1985. The contribution of low birth weight to infant mortality and childhood morbidity. N Engl J Med 312: 82–90
7) Goldenberg RL, Hauth JC, Andrews WW. 2000. Intrauterine infection and preterm delivery. N Engl J Med 342:1500–1507
8) Ferguson KK, Loch-Caruso R, Meeker JD. 2012. Exploration of oxidative stress and inflammatory markers in relation to urinary phthalate metabolites: NHANES 1999-2006. Environ Sci Technol 46: 477-85.