Environmental Toxins and Child Development
By Dan Orzech
Social Work Today
Vol. 7 No. 2 P. 37
Developmental disability organizations join forces with environmental groups to persuade government and industry to examine the effects of toxic chemicals on child development.
We are adrift in a sea of chemicals. In the last half-century or so, more than 85,000 industrial chemicals have been registered in the United States, and many of them have found their way into our environment—and our bodies. Children, with their smaller and still-developing bodies, may be the ones most vulnerable to their effects.
For decades, environmental groups have struggled to convince government agencies and industry to consider the effects of these environmental toxins on children. Now, they are getting help from a new—and perhaps unexpected—direction: groups such as the Autism Society of America, the Learning Disabilities Association of America, and the American Association on Intellectual and Developmental Disabilities, formerly the American Association on Mental Retardation. These organizations, and dozens of others, have teamed up in an effort called the Learning and Developmental Disabilities Initiative, aimed at protecting children from pollutants that may undermine brain development.
There’s a growing body of evidence making a connection between how well children perform in school and life and toxins in their environment. Lead poisoning, for example, has been shown to lower IQ and shorten attention spans. Children with high levels of lead in their body have more trouble concentrating and following directions and tend not to do as well in school. They are also more prone to impulsivity and antisocial behavior, including violence.
Most mental health professionals are probably aware of what lead poisoning can do to children, says Mary Rogge, PhD, associate professor of social work at the University of Tennessee, who conducts research on children and chemicals in the environment. But there are a host of other chemicals in the environment and many social workers and other helping professionals, Rogge says, are unaware of the impact these toxins may be having on children’s developing neurological and other systems.
Environmental Toxins: Frighteningly Commonplace
Environmental toxins which can affect children are frighteningly commonplace. Besides lead, there are other heavy metals such as mercury, which is found frequently in fish, that are spewed into the air from coal-fired power plants, says Maureen Swanson, MPA, director of the Healthy Children Project at the Learning Disabilities Association of America.
Mercury exposure can impair children’s memory, attention, and language abilities and interfere with fine motor and visual spatial skills. A recent study of school districts in Texas showed significantly higher levels of autism in areas with elevated levels of mercury in the environment. “Researchers are finding harmful effects at lower and lower levels of exposure,” says Swanson. “They’re now telling us that they don’t know if there’s a level of mercury that’s safe.”
Chemicals in pesticides are also a major source of concern. One class of pesticides, called organophosphates, has been associated with various kinds of cancer and hormonal disruption. Approximately 40 different organophosphate-based pesticide products are currently on the market in the United States. One, called Chlorpyrifos, sold under the name Dursban, was used on school grounds and playing fields, and to get rid of household pests. Although Dursban is no longer sold in the United States, says Rogge, that doesn’t mean it’s not present in the environment. “At the time of the ban,” she says, “stores put Dursban on sale, and people stocked up. So they may still be using it.”
Another class of chemicals, organochlorines, have mostly been phased out in the United States. One of these chemicals, Lindane, was available as recently as 2003 as a prescription medicine to eliminate head lice and was associated with symptoms such as dizziness, headaches, and convulsions. Another organochlorine, dioxin, found in pesticides such as dichlorodiphenyltrichloroethane, has been banned from sale in the United States for some years. But dioxin, says Rogge, still enters the environment as a byproduct of combustion from industrial processes.
Other chemicals that have also been banned from use may still be causing problems as well. Polychlorinated biphenyls (PCBs), some of which are a form of dioxin, for example, have been banned in the United States for years but are still found in the environment. Researchers have found evidence that children exposed in the womb to low levels of PCBs grow up with poor reading comprehension, low IQs, and memory problems.
Then there’s a whole category of chemicals that are known or suspected endocrine disruptors. These chemicals can interfere with the human hormonal system, particularly the thyroid gland, says Swanson. During pregnancy, the hormones released by the thyroid are vital for normal development of the fetus’ brain.
Unfortunately, some of these chemicals make good flame retardants and have been widely used in everything from upholstery to televisions to children’s clothing. Studies have found them in high levels in household dust, as well as in breast milk. Two categories of these flame retardants have been banned in Europe and are starting to be banned by different states in the United States.
Other chemicals, called plasticizers, are just now coming onto the radar screen as possible sources of health problems. One of them, bisphenol A, is found in pacifiers, baby bottles, and dental sealant used to prevent cavities in children. It’s also found in many adult consumer products, according to Elise Miller, MEd, executive director of the nonprofit Institute for Children’s Environmental Health and national coordinator of the Learning and Developmental Disabilities Initiative. “We all have bisphenol A in our bodies now,” she says. Research on bisphenol A has shown it can affect both the reproductive and neurological system, and that it appears to accumulate at higher concentrations around the fetus—in the umbilical cord and amniotic fluid—than in the mother’s blood.
Fierce Debates
Much of the science in this area is new, and much of it is still being debated by researchers. A fierce controversy, for example, has surrounded the possible connection between the use of mercury as a preservative in children’s vaccines and autism. A 2006 ban by the city of San Francisco on the use of chemicals called phthalates in children’s toys is now headed to the courts. Rogge and others in the field, therefore, are careful to distinguish between research showing an association between an environmental toxin and children’s health and studies that show a clear causal relationship.
While the body of scientific research on the subject is growing rapidly, much is still unknown. “Of the tens of thousands of chemicals that have been introduced into the environment in the last half-century,” says Miller, “most have not been tested for human health problems—and only 15 have been thoroughly tested for neurotoxicity.”
Nor has there been much research on the consequences of being exposed to multiple toxins. “Almost all of the testing has looked at individual chemicals,” Miller says. “We have very little understanding of how they might act in combination. We’re way behind in understanding synergistic impacts.”
The scientific research that does exist, however—and simple common sense—points to a problem.
“We all have hundreds of chemicals in our bodies today that didn’t exist a few decades ago,” says Miller. “And we’re seeing increases in learning and developmental disabilities as well as many other chronic diseases. Currently, one in six children under the age of 18 have some kind of learning, or developmental, or behavioral disorder.”
While there’s debate about just how much of that is an actual increase, and how much may be due to factors like better diagnosis, people who have worked with children for a long time are seeing a change, according to Miller.
“I talk to a lot of teachers,” she says, “and any of them who have been in the classroom the last 20 or 25 years will tell you, ‘I used to have one kid or two kids who had learning problems or were disruptive, and now, half my class has behavioral issues.’ That’s not necessarily all because of environmental exposures, but genes don’t change that quickly. So social, nutritional, and environmental factors have got to be playing a significant role.”
More Vulnerable, Pound for Pound
While much research remains to be done, one point has become clear: children are far more vulnerable to toxins in the environment than adults.
Studies have shown, for example, that children living in homes contaminated with pesticides had almost twice as much of the chemical in their blood as their parents. And in a home with radon, a 6-month-old child will receive twice the exposure as an adult, according to the World Health Organization.
That’s due, in part, to children’s higher metabolic rate, says Rogge. Pound for pound, children breathe more oxygen and consume more fluids and food than adults. A typical infant drinks six ounces of formula for every kilogram of body weight. That’s the equivalent of an adult male drinking 35 cans of soda per day. If the air or food is contaminated, they will receive more of it relative to their size than adults.
Children also have a greater skin area relative to their volume than adults, increasing their vulnerability to physical contact with environmental toxins such as formaldehyde, which is found in carpets and pesticides applied to grass. And children, of course, typically spend far more time on the floor and in the dirt than adults.
Children are also more vulnerable because they are still growing. Key organ systems such as the brain and nervous system, lungs, and reproductive organs are all still developing rapidly in the first few years of life, making them susceptible to interference from toxic chemicals. In addition, the kidneys and liver are not fully developed and can’t detoxify harmful substances as well as those of adults.
Children are exposed to environmental toxins in various ways. School buses, for example, which shuttle millions of children between home and school every day, routinely trap alarmingly high levels of diesel exhaust inside, according to a study conducted by the National Resources Defense Council, the Coalition for Clean Air, and the University of California, Berkeley. And numerous studies have shown that diesel fumes cause cancer, particularly lung cancer.
In one study of baby foods sold in the United States, more than one half of all samples contained detectable levels of pesticides. Nearly one fifth of baby food jars examined contained two or more pesticides.
Food is not the only item children put in their mouths. Children, by nature, explore their environment, often by putting dirt, paint, or other non-food substances into their mouths, potentially exposing them to environmental toxins.
Exposure can come from unexpected—and sometimes tragic—sources as well. The growing amounts of illegal methamphetamine being produced in the United States, often in people’s homes, require up to one dozen dangerous chemicals for their production process.
According to the National Drug Intelligence Center, more than 700 children present when police raided methamphetamine laboratories in 2001 tested positive for toxic levels of chemicals in their bodies.
Still Getting the Lead Out
One area that has seen considerable success is the effort to reduce lead poisoning in children. The federal government banned the use of lead in paint in 1971, and later in gasoline and food cans. That substantially reduced children’s exposure to lead: between 1976 and 1991, the percentage of children in the United States with dangerous levels of lead in their blood had fallen from 88% to less than 5%.
Unfortunately, that doesn’t mean the problem is gone. “Many people believe that the problems with lead have been dealt with,” says Rogge. “That’s not the case. There’s still lead in old housing and other places, such as lead that has accumulated in soil. While we don’t put lead in gasoline anymore, it’s one of those chemicals that hangs around in the environment.”
There are, in fact, still nearly 1 million children in the United States with high levels of lead in their blood, according to Miller. Children from low-income families or who live in inner cities are affected disproportionately, says Miller. But the problem can pop up anywhere: schools in Seattle and Washington, D.C., were in the headlines in the past year when lead was found in their water pipes.
In western New York, lead is a regular issue in the clinical practice of Nicole Kelly, LMSW, a social worker at a local chapter of the Learning Disabilities Association of America. Kelly, who helps families document their needs to receive services from state agencies, runs into several cases each month of children who have had lead poisoning. “When we’re doing an intake,” she says, “one of the questions we routinely ask is whether the child has ever been exposed to lead or other toxins.”
In New York State, every child must be tested for lead at ages 1 and 2. Documenting lead poisoning, Kelly says, particularly in a serious case where the child had to have chelation therapy to remove lead from the blood, can show a possible cause for a learning disability and help make a stronger case for access to state services.
Heredity, Environment, or Both?
While the toxic effects of lead are undisputed, scientists and policy makers who focus on environmental toxins are wrestling with many situations which are far more complex. A fierce debate on the possible causes of autism, for example, has pitted genetics against environmental toxins such as mercury. One emerging area of study, says Swanson, is the connection between these two along with a number of other factors, including nutrition. “We know autism has a strong genetic component,” she says, “but researchers are now studying whether the increase in autism rates might be linked to a combination of genetic susceptibility and environmental factors. It might be that if children with this particular genetic susceptibility are exposed to low levels of mercury and eat gluten and dairy, it may trigger autism. Several major research centers are looking into this, and study results already suggest it’s not just environmental factors and it’s not just genetics—it’s probably a nexus of both.”
Other areas of research are emerging as well. One of these areas, says Miller, are the connections between environmental exposures and mental health issues. While there’s not much research yet on the subject, she says, there is some evidence of a link between lead and pesticides in the environment and schizophrenia, anxiety, and depression. The nonprofit National Association for the Dually Diagnosed, which helps people with developmental disabilities and mental health needs, has joined the other groups in the Learning and Developmental Disabilities Initiative focusing on environmental toxins.
“It’s a whole new arena,” says Miller, “but it certainly makes common sense that if exposure to an environmental toxin affects your neurological systems, it’s not just going to manifest as a developmental issue; for at least some people, it may manifest as a mental health issue.”