Lead Levels Tied to Aggressive Behavior 

ANGELA STEWART / Star-Ledger (Newark, NJ) 17jun03

[Abstract below]

There is a direct relationship between environmental exposure to lead and aggressive and even violent behavior in humans, New Jersey researchers conclude in a new study released yesterday.

The study, conducted on a small sample of laboratory animals by researchers at the UMDNJ-New Jersey Medical School in Newark, appears in the July issue of Environmental Research. It was funded by the National Institutes of Health and gives weight to previous studies that have linked lead exposure and lead poisoning in humans to aggressive behavior.

"Other epidemiologic studies have been strongly suggestive of such a relationship, but could not rule out other factors. This study demonstrates a direct cause and effect relationship between lead exposure and the tendency to behave more aggressively," said lead researcher John D. Bogden, professor of preventive medicine and community health at the medical school.

Lead poisoning is the most prevalent pediatric disease of environmental origin in the United States. In New Jersey, thousands of children have enough lead in their blood to impair their ability to think, concentrate and learn. The state's first comprehensive report on lead released in 2001 showed that 5 percent of children tested in fiscal year 2000 had a blood level at or above 10 micrograms per deciliter, which is considered elevated.

In children 3 and under, lead alters the cell structure and chemistry of developing brains, often resulting in lower intelligence, hyperactivity and increased aggression.

Pediatric lead poisoning results primarily from the ingestion of very small quantities of lead from environmental sources, primarily paint chips, dust and soil, but also from drinking water and many other sources.

To carry out their study, researchers placed small amounts of lead in the food of five cats to measure the effects. They then conducted trials in which predatory attack behavior of the animals was measured by applying small electrical impulses to a region of the brain that controls behavior.

Currents were measured three times per week for a total of six to 10 weeks, including, before, during and after lead exposure. Bogden said the research found that with lead in their systems, three of the five cats were much more aggressive than before or after their exposure to lead.

"The lead made it (aggressiveness) happen more readily and at a lower current," he said.

Although removing the lead source from the animals in the study decreased their level of aggressiveness, one cannot necessarily make the same application to humans, the researchers warned.

"There is evidence that once you get lead in the brain, some of the effects are irreversible," said Donald B. Louria, chairman emeritus of the department of preventive medicine and community health at the medical school, who also worked on the study, along with Allan Siegel, professor of neurology and neurosciences.

All five animals involved in the study survived the experiment and suffered no permanent damage, he said.

Experts said the study's significance in showing a direct relationship between lead and anti-social behavior should not be understated.

"It really backs up some of the stuff we have been talking about for years. It is important data and makes the case that we should not only be screening kids for lead, but trying to prevent them from getting it in the first place," said Steven Marcus, director of the New Jersey Poison Information and Education System.

Lead exposure potentiates 
predatory attack behavior in the cat 

Environmental Research v.92, i.3, Jul03

Wenjie Li^a, Shenggao Han^a, Thomas R. Gregg^b, Francis W. Kemp^a, Amy L. Davidow^a, Donald B. Louria^a, Allan Siegel^b and John D. Bogden* ^a

a Department of Preventive Medicine and Community Health, UMDNJ––New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103-2714, USA

b Department of Neurosciences, UMDNJ––New Jersey Medical School, 185 South Orange Avenue, Newark, NJ 07103-2714, USA

Received 25 March 2002; revised 27 September 2002; accepted 22 November 2002. ; Available online 29 March 2003.

Abstract

Epidemiologic studies have demonstrated that environmental lead exposure is associated with aggressive behavior in children; however, numerous confounding variables limit the ability of these studies to establish a causal relationship. The study of aggressive behavior using a validated animal model was used to test the hypothesis that there is a causal relationship between lead exposure and aggression in the absence of confounding variables. We studied the effects of lead exposure on a feline model of aggression: predatory (quiet biting) attack of an anesthetized rat. Five cats were stimulated with a precisely controlled electrical current via electrodes inserted into the lateral hypothalamus. The response measure was the predatory attack threshold current (i.e., the current required to elicit an attack response on 50% of the trials). Blocks of trials were administered in which predatory attack threshold currents were measured three times a week for a total of 6–10 weeks, including before, during, and after lead exposure. Lead was incorporated into cat food "treats" at doses of 50–150 mg/kg/day. Two of the five cats received a second period of lead exposure. Blood lead concentrations were measured twice a week and were <1, 21–77, and <20 µg/dL prior to, during, and after lead exposure, respectively. The predatory attack threshold decreased significantly during initial lead exposure in three of five cats and increased after the cessation of lead exposure in four of the five cats (P<0.01). The predatory attack thresholds and blood lead concentrations for each cat were inversely correlated (r=-0.35 to -0.74). A random-effects mixed model demonstrated a significant (P=0.0019) negative association between threshold current and blood lead concentration. The data of this study demonstrate that lead exposure enhances predatory aggression in the cat and provide experimental support for a causal relationship between lead exposure and aggressive behavior in humans.

Keywords: Lead; Aggression; Predatory attack; Cat; Violence

* Corresponding author. Fax: +973-972-7625 bogden@umdnj.edu