The Autoimmune Epidemic: Bodies Gone Haywire in a World Out of Balance--and the Cutting-Edge Science that Promises Hope (No Series) (9 page)

THE DANGER OF TINY DOSES

Dioxin, along with pesticides, insecticides, and plasticizers such as bisphenol A, or BPA, a plastics building block used in everything from safety helmets, dental sealants, and eyeglass lenses to everyday food packaging, are what are also known as endocrine disruptors, a group of environmental contaminants that can affect our immune system and our resistance to disease in another particularly insidious way—and in particularly small doses—by disrupting our bodies’ natural hormonal signals.

Animals and humans secrete minuscule amounts of hormones, such as estrogen, that trigger responses when they occupy special receptors made to receive them on the cells of various organs in our bodies. These hormones are secreted into the blood by the endocrine glands that produce them—the thyroid, pancreas, and adrenal glands, as well as the ovaries and testes—in response to signals from the brain. Chemicals like PCBs, plastic additives such as BPA, and common pesticides are among the numerous chemicals that, upon entering our bloodstreams through daily exposure, can mimic estrogen by occupying our cells’ estrogen receptors.

You might think of estrogen being secreted in the body as something akin to a radio signal that’s being sent out from a station, and its receptor—a protein on the surface of a cell elsewhere in the body—as the antenna. The proper signal has to reach the antenna in order for the signal to be received—and for music, rather than static, to come out of the radio. When endocrine disruptors mimic real estrogen they can wreak havoc in one of two ways: first, they can block the estrogen receptor site altogether, keeping our natural estrogen from triggering the responses it’s supposed to so that it can do its normal job in the body. When estrogen signals are blocked, it prevents our hormones from sending out any signal at all. The second way that endocrine disruptors work is not by blocking communication completely, but by sending the wrong signals between cells.

Researchers now understand that a wide array of environmental chemicals can act as endocrine disruptors, affecting us at much lower doses than scientists previously thought possible. A growing body of new science on low-dose exposures suggests to investigators that even minute traces of many common chemicals—at levels that have been touted by industry and some scientists to be biologically safe—can affect our cell activity by sending out artificial messages to the body through our endocrine system.

Endocrine-disrupting chemicals are remarkably adept at traveling through the bloodstream and entering our cells by tricking specific receptors on cells into believing that the chemicals are, in fact, real estrogen being secreted by our own bodies (endocrine literally means “secreting internally”). Once in the cell, these chemical imposters bind with estrogen receptors and begin to set things askew by sending out a false signal to the rest of the body—one that the brain did not intend or command. It is as if the radio waves have been hijacked by a rogue station. Suddenly, instead of music emerging from the radio, these imposters send out scrambled signals—a completely different kind of sound. The cells in the body begin to respond inappropriately, acting as if they’ve been signaled by real estrogen to cause other cellular interactions to take place when in fact these exchanges are not what the body intended at all. The cells begin to dance to the wrong tune—engaging in precarious missteps.

When this normal cellular interaction begins to go haywire at major phases of development—say, when Becky’s son Zachary was developing in her womb, or while his infant brain is maturing, or in eight or so years when Selena comes into puberty—these artificial chemicals usurping the place of natural estrogen can trigger unnatural biological responses. Scientists have worried for decades about data showing endocrine disruptors’ effects on the brain and the reproductive system. As we learn more about how these chemicals interfere with cellular signaling in the body, endocrine mimickers have become a grave concern to scientists studying autoimmune disease.

Dr. Allen Silverstone, a professor of microbiology and immunology at the State University of New York Upstate Medical University at Syracuse, has been demonstrating in the lab how endocrine disruptors disturb the regulation of the immune system, given the profound influence the endocrine system has over the workings of our immune cells. When our endocrine system’s exquisite communication network goes on the blink, the immune system’s network can go haywire as well.

Silverstone, an unassuming sixty-four-year-old immunologist whose own wife has suffered greatly from rheumatoid arthritis, began to investigate the role of endocrine disruptors on the immune system after developing successful target therapies for childhood leukemia. “I thought cancer was messy,” he says. “But autoimmunity is so much messier.”

One particular endocrine receptor interests Silverstone in particular. In 1979 a new receptor was discovered, called the aryl hydrocarbon receptor, which binds specifically with dioxin and PCB. The aryl hydrocarbon receptor is found in almost every tissue of the body and it is found far down the evolutionary chain, even in fish. Even though we’ve known about this protein for nearly thirty years, says Silverstone, we “still don’t have a good idea of what it normally does.” But scientists know this much. When dioxin enters the body and binds with this receptor, says Silverstone, “it’s like a bad accident happening in the body. Dioxin and PCB bind very tightly with the aryl hydrocarbon receptor and keep it turned on for way too long.” That, in turn, causes the body to turn on other cellular interactions that it shouldn’t turn on, which can result in altered immunity, including autoimmune disease. Different chemicals bind with different receptors—be they estrogen receptors, androgen receptors, insulin receptors, and so on—and not only block the receptors, but begin to send out false information to other cells, creating a cascade of misinformation.

At the University of Tokyo, a team of eight Japanese immunotoxicologists recently demonstrated that in mice, endocrine-disrupting chemicals, such as BPA, promote a significantly increased production of autoantibodies—antibodies that set out to destroy one’s own tissue. Other lab research confirms that environmental estrogens, including plastic additives, exert a direct effect on immune cells, suppressing the function of some immune cells and overstimulating others. BPA, which is also used in baby bottles and in the resins that line food cans, has been discovered by the CDC in 95 percent of human urine samples tested and has been detected in newborn umbilical cord blood the world over.

In 1988, the EPA set a daily safe limit for humans of 0.05 milligrams of BPA per kilogram of body weight. Since then, investigative techniques for determining cell dysfunction in the lab have dramatically improved, allowing researchers to look at many chemicals’ subtler effects. As it turns out, a number of studies show that BPA alters the activity in animal and human cell cultures at just one twenty-five-thousandth of the dose that the EPA deemed caused adverse health effects twenty years ago. Over the past two decades, BPA has meanwhile become an integral chemical in the packaging of millions of food products and other plastic goods; more than 6 billion pounds of BPA are used each year in resins lining metal cans, food packaging, hot beverage cups, and in blends with other types of plastic products. Lab research shows that the bond that secures BPA molecules to food and beverage packages changes over time, resulting in the release of free BPA into the food we eat and the beverages we consume, as well as into the environment. In 2006, researchers found that BPA—at concentrations lower than those already found in pregnant women, fetuses, and adults, and well within the range of our typical human exposure—causes estrogen receptors to initiate unnaturally rapid responses, changing our basic cellular function. Significant effects can be seen at extremely low levels of exposure—parts per billion and even per trillion—levels currently present in blood samples taken from people as well as animals.

Chemical manufacturers have worked hard to counter the mounting academic research showing that the negative health effects of endocrine disruptors can be seen at extremely low levels of exposure. In 2004, one researcher counted up all of the studies done to date on just BPA. Of 104 studies done by independent researchers, 94 found adverse effects. None of 11 studies conducted by the chemical industry’s researchers on BPA identified adverse effects.

In the wake of the mounting data that endocrine disruptors wreak havoc on the human immune system, in 2005 the National Institutes of Health stated that investigations of exposures to pesticides and estrogenic compounds as triggers of autoimmune disease—about which we still know far too little—are now of “considerable research interest.”

Another well-known endocrine disruptor comes in the form of a group of chemicals known as phthalates, which are added to cosmetics to make them creamier, to plastic bottles and plastics in general to make them more flexible and less brittle, to children’s toys to make them more pliable, as well as to insecticides. As Becky heated up Zachary’s baby bottle, and as she warmed up her soup in the microwave, she increased the likelihood that phthalates would leach from the plastic bottle and prepackaged plastic soup container into her lunch and Zachary’s twice over: once from the bottle, and again through the trace phthalates mainlined to Zachary through her breast milk.

Whenever we heat plastics, we increase the likelihood of leaching out chemicals. Some drinking straws carry the warning on the label “not for hot beverages” for good reason: if you put that straw into a boiling cup of hot cocoa, you are creating something akin to a hot-water extraction technique—not unlike that used in labs to help isolate and draw out chemicals—causing the chemicals in the straw to be jettisoned directly into your yummy cup of cocoa. (As an aside, while urban myth holds that freezing water in plastic bottles draws out toxic chemicals and laces the water with them, in fact, freezing actually works against the release of chemicals, because chemicals do not diffuse as readily in colder temperatures.)

Phthalates are also key ingredients in Becky’s newly purchased U.S. manufactured cosmetics (whereas in Europe and Japan phthalates have been banned because of their health risks). Every day when Becky puts on her face cream and body cream, she is lathering phthalates across the largest organ of her body. Like dioxin, bisphenol A, PBDEs, and pesticides, phthalates have been found in every American tested.

Becky Sandler might be especially disturbed to learn of data linking hair dye to a woman’s likelihood of developing lupus, given that she has her roots dyed auburn to cover her premature gray every six weeks. Several studies have shown that women who use hair dye have three times the risk of developing lupus—that is, if they also carry specific genes that make them susceptible to autoimmune disease in the first place. This might not, however, reassure Becky all that much. She already has Raynaud’s disease, an autoimmune disease that is certainly mild, but nonetheless shows her personal proclivity to autoimmunity. Most sufferers of any one autoimmune syndrome are three times more likely than others to develop additional autoimmune diseases down the road.

Of the many chemicals Becky is exposed to during her day, the one that is most directly linked to the exacerbation of autoimmune disease is the paint remover she uses to strip her daughter’s chair and table. Although Becky is not a frequent user of solvents—and has little reason to fret over a one-time use in her garage—frequent use of paint thinners, removers, and mineral spirits by those who use them in occupations such as dry cleaning or airplane manufacturing (to degrease parts) or in the leather industry (to strip and tan hides) have been linked in occupational studies to a two-to threefold risk of developing multiple sclerosis, connective tissue diseases, and the autoimmune disease scleroderma.

The problem is, Becky is breast-feeding. And that means that although her exposure to chemicals may be at one level, the exposure she passes on to Zachary exists at quite another. While it may seem counterintuitive, babies nurse at the top of our food chain. They feed one rung higher than we do, and in what is known as the law of biomagnification, that means that they receive a more concentrated level of all the contaminants that we have been exposed to over the course of our own lifetimes.

Noshing at the top of the food chain, we all receive a concentrated level of the environmental chemicals that persist in the air, water, and ground—because these contaminants have been ingested by all the animals that feed underneath us at each step, all the way down to the plants that grow in soil nourished by groundwater that has been steeped in industrial runoff before being eaten by the cow in the field. Or consider the mako shark that fed on the barracuda that fed on the fish that fed on the lugworms and tiny shrimplike crustaceans that dined on the tiny granular fragments of plastic that have been steadily accumulating in the environment over the past forty years. Fibrous bits of nine different synthetics—fragments from the gradual breakdown of larger plastic items like food packaging—are now routinely found in sediment in marine habitats from sandy beaches to the bottom of the open seas. When Becky eats a dinner of mako shark in a pepper crust at her favorite seafood eatery, she is ingesting those plastics as well as traceable levels of the highly active contraceptives—from the excretion of birth-control pills through our sewage system—that also now appear regularly in test samples of U.S. seawater. These industrial compounds—both of which are known endocrine disruptors—magnify in intensity as they are passed up the food chain from host to host, reaching their second to highest concentration in us—and their highest of all in human breast milk. And because babies eat far more for their size than do grown-ups, their dose of contaminants per meal is much greater than our own. Pound for pound, breast-feeding babies get more contaminants per meal, at more concentrated levels, from the healthiest known food source on the planet.