Health Impacts of Phthalates, Polystyrene, and Other Chemicals Used to Make Plastic
In addition to its effect on soil, water, animals and the oceans, plastic--or rather the chemicals used to make plastic--has been shown to have a direct, negative impact on human health. In recent years, phthalates and polystyrene have consistently made headlines as various studies have emerged solidifying the link between these chemicals, common in many plastics, and various health problems, including cancer, diabetes, obesity and ADD.
Many thanks to Breast Cancer Fund for providing much of the information here on pthalates.
Phthalates are a group of endocrine-disrupting chemicals commonly used to render plastics soft and flexible. They are found in a wide variety of common products including plastics (e.g., children’s toys), cosmetics, pharmaceuticals, baby care products, building materials, modeling clay, automobiles, cleaning materials and insecticides. Phthalates are readily absorbed through the skin and can also enter the body through ingestion, inhalation or medical injection procedures.
Phthalates have been found in indoor air and dust and in human urine and blood samples. National data collected by the CDC show that levels are highest in children ages 6 to 11 and in women, and that blacks have higher levels of phthalates than do whites (CDC, 2005). Phthalates have also been detected in human breast milk and urine. Phthalates cross the human placenta, exposing fetuses to the hazards associated with exposure to an important class of EDCs during this critical period of development. Young infants are also exposed to high levels of phthalates, with measurable levels of seven different phthalates being found in infants born between 2000 and 2005.
Phthalates are considered to be endocrine disruptors because of their complex effects on several hormonal systems including the estrogen and androgen hormone systems. Some phthalates, including butyl benzyl phthalate (BBP) and di-n-butyl phthalate (DBP), act as weak estrogens in cell culture systems. They can bind to estrogen receptors (ER), induce estrogen-appropriate cellular responses and act additively with estradiol in altering these systems. Phthalates also bind weakly to the androgen receptor (AR), disrupting the cellular actions ordinarily initiated by the androgens (Borch, 2006). Those that bind most strongly to the AR, and therefore might be expected to exert the greatest effects through this pathway, include DBP, di-i-butyl phthalate (DiBP) and butyl benzyl phthalate (BBP).
The endocrine-disrupting properties of this class of chemicals have been well established in the offspring of mother rats who had been treated with phthalates while pregnant. Phthalates have been shown to disrupt the development and functioning of male and female reproductive systems by interfering with the production of testosterone and estradiol, respectively. Abnormalities in male offspring exposed prenatally included nipple retention, shortened ano-genital distance and increased cryptorchidism (undescended testes). Exposure of human mothers to phthalates, as measured by analysis of their urine samples, has also been associated with shortened ano-genital distances in their newborn sons—a measure of feminization of external genitalia.
A recent case-control study examined phthalate levels in apparently healthy girls who went through thelarche (breast development) before the age of 8, as compared with girls who underwent precocious puberty because of abnormalities in their neuroendocrine systems and with girls who were progressing through puberty at normal ages. Increased levels of monomethyl phthalate (MMP) were associated with early thelarche group, but not either of the comparison groups. Early breast development in otherwise healthy girls is associated with an increased risk for breast cancer.
Polystyrene is a composite material made out of the monomer styrene. It is a versatile material and can be molded into a number of different consumer products, but is normally used for food service wear. Popular uses for polystyrene include plates, cups, bowls, and to-go food containers. As a material, styrene is a known carcinogen in lab animals, and has a high liklihood for producing the same effects in humans. Currently, the FDA permits styrene to be used as a direct food additive, and it readily migrates from food packaging into the food itself.
The US EPA reports that 100% of humans have styrene in their bodies, originating from contact through food containers, inhaling indoor smoke, or drinking contaminated water. Everyday exposure can range from 1 µg/person/day to >100 µg/person/day, but occupational exposure can be much greater, occurring in polystyrene factories, the reinforced plastics industry, and in boat making.
The carcinogenic effects of styrene include elevated rates of lymphoma, hematopoiesis, and leukemia in reinforced plastics workers, primarily through inhalation. Exposure to styrene can also cause mucous membrane irritation, eye irritation, gastrointestinal effects, listlessness, impairment of balance, and central nervous system disorders such as depression, headache, fatigue, and muscle weakness among many others. In animal studies, styrene has been found to cause hearing loss, changes to the lining of the nose, and liver damage. In vitro studies in mammals have found mutagenic effects in cell cultures, which could mean complications with pregnancy and birthing later on.
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· Study: Even BPA-Free Products Leach Endocrine-Disrupting Chemicals, Time, March 2011
· Beyond BPA: Could 'BPA-Free' Products Be Just as Unsafe? The Atlantic, April 2011
· Is the Plastic Industry the New Tobacco Industry? The EnvironmentaList, March 2011
· New research adds to indictments of BPA and pthalates, The Daily Green, January 2009
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