Screening Out Neurotoxins

In 1986, Pat Griffiths took her 18-month-old son for a routine checkup in their home town of Newark, New Jersey. A blood test showed he had dangerous lead levels. Griffiths was surprised. In 1978, lead content in paint was limited to 0.06% by weight, a level that eliminates lead poisoning dangers from new paint. And lead in the environment from gasoline emissions declined markedly after the auto industry switched to catalytic converters in 1975 and leaded gasoline was phased out, beginning in 1979.

But Griffiths' toddler, as well as her two other sons, lived in a house with old lead paint on the walls, and played in soil with high lead levels, contaminated by years of lead settling from the air. The paint removal ordered by their landlord increased the boys' blood lead levels even more, Griffiths believes. Twelve years later, their levels are down, "but the damage is already done," she says. Her three sons all suffer long-term health problems because of lead.

Lead is a potent neurotoxin, as are other heavy metals such as mercury and cadmium, and certain pesticides, industrial chemicals, and polychlorinated biphenyls (PCBs). Neurotoxins, which attack the nervous system, are especially hazardous to fetuses and children. High exposures can result in brain damage. The most commonly occurring and dangerous neurotoxins are listed below.

No Safe Lead Exposure

Exposure to lead, even at low levels, has been linked to myriad health problems. These include impaired attention, hyperactivity, learning disabilities, behavioral problems including aggression, and decreased IQ scores. In the 1960s, blood lead levels of up to 60 µg/dL (meaning micrograms per deciliter) were considered safe, because there were no overt symptoms of poisoning below this level. But children are affected by lead at levels much lower than previously thought. Today, the Centers for Disease Control and Prevention (CDC) sets the lead safety threshold at 10 µg/dL for blood. The CDC estimates that 890,000 children under the age of six (4.4% of pre-schoolers) have blood lead levels equal to or greater than this standard. "I think it's amazing that we have almost one million children with a neurotoxin, a brain poison, in them, and we are largely silent," says Andrew McBride, M.D., M.P.H., Assistant Secretary for Health and State Health Director for North Carolina.

"You don't have to be physically ill with lead poisoning to show [developmental] deficits because of it," says Herbert Needleman, M.D., Professor of Child Psychiatry and Pediatrics at the University of Pittsburgh and a leading lead researcher. In one long-term study of 132 children in Massachusetts in 1989, Needleman found that those who had been exposed to the highest lead levels during their early years developed reading disabilities at six times the rate of those with the lowest lead levels, and dropped out of high school at seven times the rate of those with the lowest levels.

Pat Griffiths says she sees the long-term effects of lead poisoning every day. "Memory is a real problem for my children," she says. "Brian's an all-star catcher, and he'll show up for a 1 p.m. practice at 8 a.m. He doesn't want to be late, but he doesn't understand the concept of time." And Cordell Cleare, co-chair of the New York City Coalition to End Lead Poisoning, says that taking care of her five-year-old son, who was diagnosed with blood lead levels around 40 µg/dL when he was two, "takes a lot of attention, a lot of repetition."

Lead Culprits

The primary source of lead poisoning in the U.S. is old, lead-based paint. Maurci Jackson, executive director of the Chicago-based Parents Against Lead, recalls how her daughter was first diagnosed with lead poisoning. "At 15 months, she ate a piece of paint off the baseboard in the bedroom. She woke up in the middle of the night, and came to me spitting it out." The next morning, "We were first in line at the clinic," where blood lead levels in the 30s were detected, Jackson says. She thinks that the persistence of lead dust in her home kept her daughter's lead levels up. It took seven years for her daughter's levels to drop below 10 µg/dL.

In the U.S., an estimated 64 million housing units (or 83% of private housing built before 1980) still contain lead paint, according to the EPA. Lead poisoning is especially difficult to eradicate in poor, urban communities, where deteriorating lead paint is more likely to be found. While landlords in some states such as California and Massachusetts are required to take corrective action, there is no federal law requiring landlords to clean up lead paint even if a child has lead poisoning. A representative for the National Lead Information Center says that in his experience, counties take action against landlords if children have high levels -- at 40 µg/dL on average. But lead is not just an urban problem. "In North Carolina, children in rural areas have higher lead levels than those in urban areas," says Dr. McBride. Nor is paint the only lead source.

Other sources of lead include: soil, contaminated by automobile exhaust from leaded gasoline, especially near highways and busy roads. According to the EPA's Toxic Release Inventory, in 1995 alone over 16 million pounds of lead and lead compounds were released into the environment by industry. Lead is also present in some drinking water, mostly as a result of lead solder used in pipe joints, and lead pipes used in and between homes.

The sources of lead poisoning can vary regionally. In the Southwest, the primary source of lead poisonings is Mexican pottery with lead-based glazes. "In Alexandria, Virginia, the number one source of lead poisoning is from 'kohl' and 'surma' eye make-up," says Janet Phoenix, M.D., M.P.H., of the National Safety Council's Environmental Health Center.

While only allowed in new paint at very low levels, lead is not necessarily regulated in other products. High levels of lead have been found in some calcium supple-ments, as well as in vinyl miniblinds, and other vinyl products. In 1997, Joseph DiGangi, Ph.D., of Greenpeace's toxics campaign, tested 131 polyvinyl chloride (PVC) kids products such as toys, backpacks and raincoats, and found that 18% contained levels of lead that violated the Consumer Product Safety Commission's staff-recommended limit. "It doesn't make sense to me to make a product for kids out of that material," DiGangi says. "The scientific consensus is that there's no safe level of lead exposure."

Mercury Offenders

Depending on the exposure, mercury poisoning can cause numbness in fingers and toes, impairment of motor coordination and speech, drowsiness, memory problems, and tremors. Mercury passes through the placenta and can accumulate in higher concentration in the unborn child than in the mother. It is used in thermometers, fluorescent lights, thermostats and some latex paints (as a fungicide). And some folk medicine practitioners illegally sell mercury. Even a few drops from a broken thermometer can cause health hazards in the home, "because mercury evaporates into the air over time and will be inhaled," according to Mary Dominiak of the EPA's Office of Pollution Prevention.

Mercury in contaminated waterways can be converted by bacteria into toxic methylmercury, which is more soluble in animal fats. This came to light in the 1950s, when a battery factory released mercury into Minamata Bay in Japan, and large numbers of infants were born with brain damage to women who had eaten contaminated fish. Mercury continues to contaminate our fresh and ocean waters through discharges from waste incinerators and coal-burning power plants. It also leaches from garbage dumps. Federal health warnings identify 1,660 water bodies as too contaminated with mercury to be fished for food.

Pesticides in Kids' Diets

Organophosphate pesticides, or OPs -- such as chlorpyrifos (Dursban™), diazinon (Spectracide™), malathion and methyl parathion -- can cause anxiety, insomnia, headache, nausea, irritability, mood swings and confusion. They are used widely in conventional farming, home insecticides, and in municipal battles against mosquitoes.

"Dietary exposure to OPs exposes many children to levels that are above the current adult-based safety standards," says Kert Davies, a pesticide specialist at the Environmental Working Group (EWG). A January 1998 report by EWG analyzed over 80,000 government lab test results and found that, every day, 9 out of 10 American children age six months to five years are exposed to OPs in the foods they eat. One out of 20 -- more than one million children -- are exposed to OPs above EPA-established "safe" levels, every day. The report used actual data, not estimates, on pesticide residues and food consumption, and was based on levels in food as actually eaten, after washing, processing and cooking.

Carbamate pesticides, including bendiocarb (Ficam™), carbaryl (Sevin™) and propoxur (Baygon™), are also neurotoxic, and cause symptoms similar to those caused by OPs.

Solvents and PCBs in Body Fat

"All solvents get into the brain," says Dr. Needleman, "because they're fat soluble." Solvents such as benzene and xylene keep paint in a liquid state and evaporate after application, when they are easily inhaled. Toluene and other solvents are used as "inert" ingredients in many pesticides. Perchloroethylene, or perc, is used in dry cleaning to dissolve grease on clothing.

PCBs, widely used as electrical insulators before being banned in 1979, remain with us in contaminated waterways like the Hudson River, Great Lakes, and Rio Grande. Joan Newman, Ph.D., an associate professor at the State University of New York at Albany, and Lawrence M. Schell, professor of epidemiology, are studying the long-term effects of PCBs on Mohawk adolescents in northern New York State. The Mohawks' exposure to PCBs comes mostly from eating fish from the St. Lawrence River. Newman and Schell are looking at low-level, pre- and postnatal exposures, and while the study is not yet complete, Newman says that, "If one is exposed to PCBs prenatally, there's reason to think it's having long-term, small-scale but important effects." These include impaired intelligence, memory and language skills throughout life.

The seriousness of the threats posed by neurotoxins, especially lead, requires government to take a tough stance. But "the CDC has no long-term plan for eliminating lead," says Dr. McBride, who points out that the CDC does not require any public health intervention until a child's blood lead levels have reached 20 µg/dL. "A restaurant can be closed if the temperature of food is not hot enough, even if there have been no cases of dysentery." But with lead, "we have to wait until we have poisoned children before we do anything," he says.

Molly Rauch, M.P.H, is a health writer in New York City. With additional reporting by Aisha Ikramuddin.