Industrial chemicals in mothers and daughters: The pollution we share and inherit
Across Generations: Findings
Chemicals in mothers and daughters. In November and December 2005, four mothers and their daughters donated blood and urine to a biomonitoring program, collecting a first morning void of urine, and rolling up their sleeves for a needle that collected blood into 10 small glass and plastic tubes with color-coded tops. From tests of these fluids they would not learn of their cholesterol, liver function, or thyroid hormones. Instead, they would uncover personal facts more unique and far more difficult to diagnose: the levels of 70 industrial chemicals circulating in their bodies at the moment the fluids were released, mixtures that have never before been tested in combination, carrying health risks that are largely unknown.
Together, the body burdens of four mothers and their daughters include seven plasticizers called phthalates (pronounced tha'-lates) used in plastic, cosmetics, and building materials; chemicals known as bisphenol A (BPA) and BADGE-40H, which are, respectively, residues from hard plastic bottles and from epoxy resins used to line food cans; a suite of brominated flame retardants used in computers, TVs, and foam furniture; perfluorochemicals related to Teflon and Scotchgard; and lead and mercury, toxic metals from chipping paint and tainted seafood.
The data are remarkably consistent with two tenets of the human body burden of industrial chemicals: levels of persistent chemicals, those that cling to body tissues for decades, build up to higher and higher levels in the body over a lifetime; while levels of non-persistent chemicals, those that pass through the body over a few days' time, vary widely and depend not on as much on age as on day-to-day contact with everyday consumer products.
Below we describe findings from this investigation, that shows for four mothers and their daughters what it means to share and inherit the body burden of industrial chemicals.
The pollution we inherit. Among the eight mothers and daughters tested, we found that an average of 93 percent of the chemicals daughters harbor in their body tissues and fluids are also found in their mothers, compared to just 81 percent held in common between daughters and 16 other women who were tested. This difference was statistically significant in three of four daughters, and emerged despite the fact that many chemicals in the study are expected to be found in most people tested, regardless of family connections. Included in this study are chemicals that rate among the most ubiquitous pollutants ever detected in people, including phthalate plasticizers, lead, mercury, brominated flame retardants, and the Teflon and Scotchgard chemicals known as PFOA and PFOS.
Studies show that a mother confers a portion of her chemical body burden to a child in the womb (EWG 2005), and continues to pass down pollution after birth through her breast milk. Studies have found that a mother passes to her child an estimated 50 percent of her own body burden of persistent chemicals through six months of breast feeding (LaKind et al 2000). The undeniable phenomenon of inherited pollution has led researchers to note that nursing a child is "the only known way" in which a women can unload from her body "large amounts" of persistent chemicals (Jorgenson 2001). Nevertheless, child health advocates are quick to note that breast milk remains the best food for babies, despite the pollution: "The advantages of breast-feeding have been documented in the neonatal period and extend throughout childhood and into adulthood" (Solomon and Weiss 2002). That no substitute for a mother's milk has been found raises deep concerns about the ubiquity of pollution in this otherwise singularly perfect infant food.
Inherited pollution that lasts a lifetime. A daughter's birth load of inherited pollution can last a lifetime, and a daughter can act as a conduit from grandmother to granddaughter, passing inherited chemicals to her own children during pregnancy and nursing. While the daughters in this study excreted an average of 99 percent of their inherited load of methylmercury by their first birthdays, similar levels of purging don't occur until adolescence, childbearing years, senior years and beyond for other pollutants even more persistent in the body, including flame retardants, Teflon chemicals, and lead. And of course, for these daughters, new exposures continue after birth and after giving birth; many of the chemicals included in this study continue to accumulate over a lifetime.
At one end of the spectrum are the plasticizers called phthalates, which pass through the body over the course of a day. Mercury is more persistent: children excrete 99 percent of their inherited load of methylmercury, on average, by their first birthday, though within that relatively short span the chemical may already have exerted its damaging effects to the developing brain. Through their natural excretion processes, daughters in this study would not reach this level of purging for brominated flame retardants and Teflon and Scotchgard chemicals until they reach ages estimated to range from adolescence to 58 years of age. And unless they live to be 166, these daughters could not rid themselves of 99 percent of the lead passed through the placenta into their bodies in the womb.
The daughters in this study range in age from 17 through 29. The science of chemical persistence tells us that at their current ages they continue to hold in their bodies, on average, an estimated 60 percent of the lead, four percent of the Teflon chemical PFOA, and 19 percent of the Scotchgard chemical PFOS passed to them from their mothers.
At age 29 at the time of sampling, the oldest daughter in this study would harbor an estimated one percent of the original mass of the Teflon chemical known as PFOA and half of the lead passed to her from her mother across the placenta. But last fall she passed a portion of this pollution on to her newborn daughter; her own loads of pollution are likely lower now. The youngest daughters in this study, at age 17, continue to store an estimated 68 percent of the lead passed to them in utero from their mothers, and 27 percent of the Scotchgard chemical PFOS.
These estimates are derived from studies which indicate that the body can rid itself of half of any given dose of mercury, PBDE-47, Teflon (PFOA), Scotchgard (PFOS), and lead in two months, 1.8 years, 4.3 years, nine years, and up to 25 years, respectively (NAS 2000, Geyer et al. 2004, Burris et al. 2002, Olsen et al. 2003, Lin et al. 2004).
An unwanted inheritance that accumulates over a lifetime. Levels of persistent brain toxins and carcinogens are higher in mothers than in their daughters. In 14 of 16 cases, mothers' bodies held higher amounts of four body-persistent chemicals or chemical families than their daughters' bodies, including lead, methylmercury, stain- and grease-resistant chemicals in the Teflon family, and brominated fire retardants known as PBDEs. The two exceptions to this trend were found in the relatively low levels of lead and perfluorochemicals found in a mother who had undergone detoxification procedures to rid her body of chemicals three weeks prior to giving blood and urine for this study.
The majority of these compounds persist in the body for years, and build up over time, a chemical property that accounts for higher levels in mothers relative to their daughters. But a mothers' higher levels can stem from a wide variety of other factors as well, including differing exposures (higher seafood consumption in mothers, for instance, can increase methylmercury pollution); higher income, which can drive higher rates of purchasing new products with flame retardants and perfluorochemicals; and physiologic differences like a diminished ability to excrete chemicals (Geller and Zenick 2005).
Just as in childhood, the later years in life are a time of susceptibility to chemical toxicity. As the body ages, it becomes not only more vulnerable to industrial chemicals, but also less efficient at metabolizing and excreting these chemicals.
As they age people can be exposed to higher amounts of some chemicals. Exposure patterns change — for instance, older adults spend more time indoors than younger adults, and during this time can be exposed to the many hazardous air pollutants found at higher concentrations indoors than outdoors. Changes in physiology with age can increase the amount of a chemical that is absorbed into the body. For example, as the skin ages, it allows more of some chemicals to penetrate into the blood vessels below.
With age also comes a reduced capacity to metabolize and excrete chemicals. EPA scientists summarize a number of these phenomena in a recent review of aging and susceptibility: decreased muscle mass and increased fat stores result in higher accumulation and reduced excretion of some chemicals; kidney function decreases with age; liver activity drops, with an accompanying potential for slowed detoxification of chemicals and reduced excretion rates.
Aging leads to physical changes that increase susceptibility to chemicals. For instance, diseases common in later life, including diabetes, hypertension, and stroke, can impair the blood-brain barrier that normally blocks many contaminants from reaching the sensitive tissues of the brain.
All these factors can result in older adults being particularly susceptible to health effects from industrial chemicals. EPA scientists summarize research showing these links between environmental exposures and disease in the elderly, including neurotoxicity, cancer, cardiovascular and pulmonary morbidity, and inflammatory responses (Geller and Zenick 2005). Increasingly, scientists are also questioning the role of industrial pollutants in a range of degenerative diseases of aging, including Parkinson's and Alzheimer's disease.