LEAD POISONING

What is lead poisoning?

 Quote Lead poisoning occurs when high amounts of lead are in the body.

This entirely preventable disease is one of the most serious environmental health hazards U.S. children face. Almost 1 million children under the age of 6 have too much lead in their bodies (more then 10 micrograms per deciliter (µg/dl)), according to the Centers for Disease Control and Prevention (CDC), the federal agency responsible for tracking disease in the United States (1). A third of these youngsters had even higher and more unsafe levels (more than 15 µg/dl).

Those most likely to have elevated blood-lead levels are children between 1 and 5 years old that live in cities, dwell in old houses, are poor, or are non-hispanic Black.

A range of symptoms accompany high lead-blood levels. However, lead symptoms vary among individuals, amount of exposure and age.



Symptoms of lead poisoning
Mild Toxicity
35-50 µg/dl in children
>40-60 µg/dl in adults		 Moderate Toxicity Severe Toxicity
70 µg/dl in children
>100 µg/dl in adults
  • Muscle (pain, tingling, pricking, burning)
  • Mild fatigue
  • irritablitiy
  • Lethargy
  • Occasional abdominal discomfort
  • Joint pain
  • General fatigue
  • Difficulty concentrating
  • Muscular exhaustibility
  • Tremor
  • Headache
  • Diffuse abdominal pain
  • Vomiting
  • Weight loss
  • Constipation
  • Partial or complete paralysis
  • Brain disfunction (seizures, unconsciousness, coma, death)
  • Lead line (blue-black) on gum tissue
  • Severe abdominal cramps
Reprinted from Lead Toxicity: Case Studies in Environmental Medicine (2) 




"Safe" blood-lead levels


There is no minimum standard of safe exposure to lead, according to the CDC. However, the CDC's 1991 guidelines for preventing lead poisoning considers blood levels greater than 10 micrograms per deciliter (µg/dl) (a microgram equals a millionth of a gram and a gram is three-hundreds of an ounce; a deciliter is about one-tenth of a quart) of blood hazardous, even though mental and physical problems can occur below this level. 


At blood levels greater than 15 µg/dl, health officials intervene by finding the lead sources and showing families how to reduce exposure. Anything above 20 µg/dl of blood is dangerously toxic and demands hospitalized medical treatment, which can include chelation therapy (a substance is injected into the blood where it attracts and binds lead and carries it from the body). Eighty µg/dl can cause convulsions, coma and even death.






Lead in the body


Lead accumulates in the body during a lifetime. Once stored, the heavy metal is released very slowly and is a continuous source of lead exposure.


In the body, lead enters the bloodstream (99 percent is associated with red blood cells and 1 percent is in the plasma) where it is carried throughout the body. Lead meets one of two fates: 1) It can be excreted through the kidneys or intestines; or 2) It can be stored in soft tissue and bones and teeth where it is slowly released over decades. 


More than 95 percent of total lead in the adult body is in bones and teeth. Throughout a lifetime, lead is mobilized back into the bloodstream in times of stress, chronic disease or pregnancy/lactation (a hazardous exposure source for unborn fetuses).


Even though single exposures are hazardous, it is chronic exposure that poses the biggest threat. Constant, long-term exposure from both the external environment and total body burden (all lead circulating or stored in a body) can cause adverse health effects. For instance, even if a person is removed from a lead source and blood-lead levels return to normal, the stored lead can be mobilized for decades, representing a continuous lead source that could cause lead poisoning. 





Lead affects health


Lead affects almost every bodily system, but susceptibility varies with age, gender and nutritional status. 


The element affects the nervous system and kidneys, inhibits hemoglobin production, interferes with vitamin D's duties in cell maturation and skeletal growth, affects fetal development and may cause renal cancer.


Most vulnerable are unborn babies and young children. The heavy metal can damage growing brains and nervous systems that have not yet formed their natural protection systems. Unborn babies are exposed through their mother's blood. Through hand-to-mouth action, children from nine months to 6 years-years-old inadvertently eat lead in paint, dust or soil. They can absorb and retain up to 50% of the swallowed element.


Once in the body, children's health effects vary. With severe lead poisoning, problems range from permanent mental retardation to death. 


Lower blood-lead levels also create a range of problems including a drop in IQ. One study found blood-lead levels of 10 µg/dl lowered IQ by 3 to 5 points. Additionally, constant exposure to low lead levels causes attention deficit, hearing loss, slowed growth, headaches and hyperactivity. 


Some of these illness go unnoticed until a child first attends school. By that time, the irreversible brain damage may be enough to interfere with life-long learning. 


Adults who live or work with high amounts of lead also suffer. Related health problems include difficulties during pregnancy, reproductive problems, muscle and joint pain, digestive problems, memory and concentration problems, nerve disorders and high blood pressure. 






Blood-lead levels declining


Overall, blood-lead levels are falling in the United States. Between 1976 and 1980, 9 out of every 10 one- to five-year-olds had lead levels greater than 10 µg/dl. Between 1988 and 1991, the same amounts were detected in only one out of every 11 children. Four years later, the number of children with high blood levels dropped again to 1 million from 1991's 1.7 million. All-in-all, the average blood-lead levels for all age groups dropped 80% since the late 1970s (3-4). 


The decreases are credited to the government mandated removal of lead from gasoline, paint, food and drink cans and plumbing systems as well as increased education and awareness programs. 


Even though blood-lead levels in U.S. children dropped between 1976 and 1991, many children, especially minority, low-income and urban youth, still face lead poisoning because of hazardous lead levels in their environment. In Baltimore, Philadelphia, Boston and Milwaukee, 35% of children have blood-lead levels higher than 25 µg/dl of blood, explains Ken Olden, director of the National Institute of Environmental Health Sciences (5).  Moreover, Rhode Island plans to open three lead treatment centers in 1997, one in the town of Central Falls where 31% of children tested had unhealthy lead blood levels. Smelterville, Idaho, which has some of the highest blood-lead levels ever recorded in humans, continues to cleanup its lead-contaminated soil, water and air (6).





References


    

  1. Update: blood-lead levels - United States, 1991-1994. 1997. Morbidity and Mortality Weekly Report. Department of Health and Human Services, Centers for Disease Control and Prevention.  46(February 21):141-146.


  2. Lead Toxicity: Case Studies in Environmental Medicine. 1992. Agency for Toxic Substances and disease Registry, U.S. Department of Health and Human Services. Publication 099-3380. 30 pp.


  3. Blood levels keep dropping - New guidelines proposed for those most vulnerable. Department of Health and Human Services, Centers for Disease Control and Prevention, National Centers for Environmental Health, Childhood Lead Poisoning Prevention. (February 21, 1997 press release).


  4. Centers for Disease Control. 1991. Preventing lead poisoning in young children: a statement by the Centers of  Disease Control. Atlanta, GA:Department of Health and Human Services.


  5. Meadows, R. 1996. Growing pains. Environmental Health Perspectives. 104(February):146-149.


  6. From a speech at Earth Day 1997 at the Center for Bioenvironmental Research at Tulane and Xavier Universities in New Orleans, Louisiana.


  7. Cleanup and lawsuits proceed in an old Idaho mining valley. Washington Post. May 5, 1997: A1,A13.


















http://www.tmc.tulane.edu/ecme/leadhome/poison.html