Environmental Toxins

Prenatal Toxic Effects

The brain in utero generates neurons at the rate of 250,000 per minute. Yet the fetus has neither a placental barrier against toxic substances nor the capacity to detoxify them. Consequently, prenatal toxic exposures can have significant effects on later health and cognitive status. Mercury exposure, for example, arrests the division of neurons, cadmium can cause brain hemorrhages, and inhalant anesthetics can interfere with cell proliferation. Lead, a long-known offender, affects the brain's blood vessels and reduces the number of neurons and dendrite connections. Low-dose prenatal lead exposure can result in preterm delivery, and higher doses can lead to spontaneous abortions. Prenatal polychlorinated biphenyl (PCB) exposure is related to IQ and attention deficits, hyperactivity, and learning disabilities years later.

Recreational drugs such as marijuana and cocaine also have known adverse prenatal effects. Maternal marijuana smoking increases the risk for premature delivery and subsequent learning problems. Cocaine causes malformation of the brain because of oxygen deprivation, intrauterine growth retardation, increased rate of preterm delivery, and genitourinary tract abnormalities. The 1,000 "crack babies" born each day in the United States face an increased risk of seizures, strokes, abnormal reflexes, poor or absent visual and auditory orientation, marked hyperactivity, irritability, distractability, delayed language and fine- motor development, and poor interactive ability later on. As infants, they are easily overstimulated. They are most calm and alert when left alone—not a very good way to encourage cognitive development.

Maternal cigarette smoking has been associated with attention deficits and hyperactivity, and mild intellectual, language, and academic delays in children. Excessive maternal alcohol consumption may lead to neurological and physical abnormalities, significant cognitive delays, hyperactivity, attention and memory problems, fine- and gross-motor delays, language deficits, difficulty with organization and problem solving, and emotional problems. As little as one drink a day during pregnancy can be harmful.

The harmful effects of the toxins mentioned are evident in both mothers and their babies. Other toxins affect the developing fetus but not the mother. These include the sleeping pill thalidomide (babies are born with missing limbs), the acne medicine Accutane (babies have severe heart deformities, abnormally small heads and eyes, and absent ears), and the antimiscarriage drug diethylstilbestrol, or DES (adult daughters have greater rates of premature birth, miscarriage, and vaginal cancer).

Postnatal Toxic Effects

The neurological, psychological, intellectual, learning, and behavioral effects of environmental toxins after birth have been well documented. Among these toxins are lead, arsenic, aluminum, cadmium, carbon monoxide, mercury, radiation, chemotherapy, illicit drugs, and solvents used in paint, glue, and cleaning solutions. Parents carry home some of these toxins on their clothing, from work or hobbies (such as stained glass work or furniture refinishing). Other toxins contaminate children through such means as pesticides, air pollution, and drugs. There has been many a heartbreak as children permanently damage their brains with licit or illicit drugs, and they are no longer the same individuals they once were. As educators, we must be aware of how toxins can impair students' development and work with parents, students, and the community to reduce the dangers that result from drug abuse, industrial hazards, and environmental pollution.

Food Allergies

It's estimated that 60 to 80 percent of individuals are allergic to at least one food. Reactions to the food may range from a mild stomachache or headache to hives and a full-blown asthma attack. Food additives (artificial colorings, flavors, preservatives), in particular, have been scrutinized as allergens related to learning disorders, especially hyperactivity. There also are reports of hyper activity after ingesting aspirin and salicylates (natural aspirinlike compounds in fruits and vegetables). Benjamin Feingold's diet, which eliminates all food additives and salicylates, has been recommended to reduce hyperactivity in children sensitive to these substances. Well-controlled studies, however, have concluded that only a very small group of hyperactive preschool children appear to respond to food additives with deteriorations in learning, behavior, and eye-hand coordination. Most children show no improvement in attention or learning when on Feingold's diet, and behavioral improvements are only slightly better than what might be expected by chance. The research concludes that although a very small group of hyperactive preschoolers can be helped by eliminating food additives and salicylates from their diets, the favorable effects reported by parents for other children are probably due to heightened expectations, increased attention to the child, and better nutritional status.

Nonfood Allergies

Despite case reports linking nonfood allergies to learning disabilities, well-designed studies have not found that more youngsters with LD suffer from allergies. Most experts conclude that allergies aggravate rather than cause learning disabilities. After all, it's hard to concentrate and do your best work when you are coughing, itching, sniffling, wheezing, didn't get a good night's sleep, and your ears are stuffed due to pollen, dust, or animal dander in the air. Ironically, the side effects of some allergy medicines may themselves complicate learning by making the child inattentive, dizzy, restless, lethargic, irritable, or hyperactive. Evidence supports the use of desensitization therapies to help students become sufficiently comfortable to attend to instruction, but the learning disability won't disappear as a result of the therapy.