Why is the Reduction of Lead from our Workplace and Environment So Important? What's Different about Lead and Lead Poisoning?
Lead is one of the few natural substances that has no use in the human body. At even very low levels, lead has been shown to cause health problems. The difficulty with lead is that once it is mined from the earth, there is no known way to destroy or make it harmless. This makes it extremely important that we reduce our use of lead and dispose of it properly.
The good news about lead poisoning is that unlike many other diseases, it is a totally preventable disease.
How Does Lead get into the Body?
Most of the lead used today is inorganic lead, and it enters the body through breathing (inhalation) and swallowing (ingestion), which are called "routes of exposure". Lead dust or particles cannot go through the skin if the skin is unbroken. (The type of lead used in gasoline is organic lead and it can get through the skin.)
For small children, ingestion is the main route of exposure. For bridge workers the main route of exposure is inhalation. However, lead dust can be ingested if it is on your hands and you smoke a cigarette or eat before washing your hands.
What Happens to Lead in the Body?
Once lead gets into the body, it is not used in any way to benefit the body. It is absorbed and distributed throughout the body. The amount the body absorbs depends on the route of exposure. In general, an adult will absorb 10-15% of the lead in the digestive system, while children and pregnant women can absorb up to 50%. People will absorb more lead if they are fasting or if their diet is lacking in iron or calcium.
When lead is inhaled, about 30%-50% of the particles will reach the lungs, depending on the size of the particle. Large particles land in the upper respiratory tract, where they get trapped by the mucous lining and moved out by hair-like objects (called cilia). Unfortunately, the mucous is often swallowed, allowing these large particles to then go into the digestive system.
Smaller particles can reach deeper in the lungs and from there be absorbed into the bloodstream. This means that when there is burning or welding on lead-painted surfaces, the lead fumes can be especially dangerous. The small particles created as a fume will reach the blood if they are inhaled.
Once lead is in the blood, some of it moves into soft tissues (organs such as the brain and kidneys). The total amount of lead that is stored in the body is called the "body burden". In adults, bones and teeth contain about 95% of the body burden. Lead that is stored in the bones can leave them and enter the blood and then the soft tissue. This can damage the organs or the blood's ability to make red blood cells. This trend may increase during pregnancy, breast-feeding and osteoporosis (the process of weakening of the skeleton in old age). It can also happen when lead is removed from the blood through medical treatment (called chelation).
How Long Does Lead Stay in the Body?
Lead stays in the body for different periods of time, depending on where it is. Half of the lead in the blood will be excreted in 25 days (this is called the "half-life"). In soft tissues, it takes 40 days for half of the lead to be excreted. In bones and teeth it takes much longer, up to 10 years or longer.
Since lead is stored in the body, a person can get poisoned from exposure to just small amounts of lead over a long period of time (called chronic exposure). You do not need to get exposed to just large doses of lead to be poisoned (called acute exposure). It can take months or years for the body to get rid of lead. A person will continue to be exposed to lead internally even after the actual exposure to lead stops.
How is Lead Measured in the Body?
Blood tests to measure the amount of lead circulating in the body were developed over 60 years ago. The results are measured in micrograms of lead per deciliter of blood (the symbols used are ug/dl or mcg/dl).
Because there is so much lead contamination of the environment, people who live in cities usually have blood lead levels as high as 15 ug/dl. This is much higher than our prehistoric ancestors who were not exposed to much lead.
The blood lead test is important for you. It gives an immediate estimate of the level of your recent exposure to lead. (Remember, it will tell you how much lead is in your bloodstream, but not what is stored in your soft tissues or bones). The test will not tell you your body burden of lead or the damage, if any, that has occurred. The blood lead test is unusual because for most toxic substances there are no tests available to tell you how much of a substance got in your body due to a recent exposure.
Another test is called the ZPP Test. ZPP stands for zinc protoporphyrin. This test is different from the blood test in that it reflects your lead exposure over a 2-3 month period. The EP (erythrocyte protoporphyrin) test is a similar test.
How Does Lead Poisoning Affect Children?
Lead enters a child's body mainly through ingestion. It is a normal part of children's play to explore and put things in their mouths. Children are more affected by lead for a number of reasons. Since their bodies are rapidly developing, they also absorb more lead than adults and their developing brains are in greater danger of being hurt by the lead.
The harder we look for lead poisoning in children, the more we find it. Over the years, the federal government has lowered the amount of lead in the blood that it defines as safe because researchers keep finding problems in children at lower lead levels.
Lead in children can affect the brain, the nervous system, the blood cells, and the child's ability to use Vitamin D and calcium.
The list that follows shows what happens to children when they have a certain amount of lead in their bloodstream.
The symptoms of poisoning usually occur in a child in 3-6 weeks. But it is important to know that many children do not show any symptoms or, if they do, the symptoms are similar to other common problems. The child may seem irritable and less inclined to play and even lose his or her appetite. The child's attention span can be affected, and children have been wrongly diagnosed as having a psychological problem. Because the nervous system is affected, the child may appear clumsy.
At higher levels, the child will probably have some vomiting, stomach cramps and anemia. If the poisoning goes untreated and is severe enough, the child's brain can be seriously affected. This is called lead encephalopathy. The child can then have bouts of drowsiness, vomiting and irritability that can be followed by seizures, coma or even death. While common 25 years ago, such cases of extreme lead poisoning are rare today.
How Big of a Problem is Lead Poisoning for Children?
Every year from 1991 to 1994, about one-million children under the age of 6 had an elevated blood lead level in the U.S. That is a rate of over 4%.
For black children, the numbers are even more distressing. Eleven percent (11%) of black preschoolers are lead-poisoned. The reason for this larger percentage is that a greater percentage of black children are poor and live in urban areas. Housing in poor neighborhoods is older and more likely to contain lead paint and be in worse condition. Also, these children may have a poor diet and not get enough iron, calcium, phosphorous or Vitamin C, all of which can increase the absorption of lead in their bodies.
How do Children get Exposed to Lead?
The major sources of childhood lead poisoning are lead paint, and contaminated house dust and soil. However, children can also be exposed to lead if their parents are exposed to lead on their jobs and bring the lead home on their clothes.
How Does Lead Poisoning Affect Adults?
Dangerous health effects or toxic effects are usually broken into two categories - short-term (acute) or long-term (chronic). Unlike asbestos, which only has chronic health effects, lead can cause both acute and chronic health effects. Below is a list of acute and chronic health effects.
Does Lead Cause Reproductive Problems in Both Women and Men?
Yes. In men, lead can damage sperm and affect the sperm's ability to move. It can affect the number of sperm that is produced in the testes. These effects on sperm can harm a man's ability to father children and have been linked to miscarriages and birth defects in their partners. These health effects can occur at 40-50 ug/dl. Some studies have also indicated that lead can affect a man's sex drive and ability to have an erection.
In women, exposure to high levels of lead may cause miscarriages, premature births, stillbirths and decreased fertility. More recently, some studies found that pregnant women with levels of lead in the umbilical cord blood of 10-15 ug/dl had children who suffer from learning and behavioral problems later in life. This is because lead in the pregnant mother's blood passes into the blood of the fetus and may affect brain development.
Possible Reproductive Health Effects of Lead in MEN
- Decreased sex drive
- Problems having an erection
- Decreased fertility
- Birth defects & miscarriages in partners
Possible Reproductive Health Effects of Lead in WOMEN
- Decreased fertility
- Miscarriages and premature births
- Learning and behavioral problems in offspring
What is disturbing for both men and women is that lead is stored in the bones. This means that past exposure to lead may affect a person's ability to have healthy children in the present. Whenever a person needs calcium, it can be drawn out of bone. It is possible that lead stored in bone can come out as well. A pregnant woman's stored lead may be drawn out of her bones because she needs calcium to build the fetal skeleton. Calcium is also needed for a mother to produce breast milk.
Currently, this puts workers who want to become parents in a tough situation. While we know more about the reproductive problems women face at blood lead levels of 10-20 ug/dl, this does not mean men do not have problems at these levels. Workers who plan to have children need to be informed of the risks in order to decide both whether to take a job involving lead exposure and for how long. If you are planning a pregnancy, you should inform your doctor about your lead exposure at work.
If you are a woman you may want to talk to an occupational medicine physician about your history of lead exposure and about having your blood lead level checked before you get pregnant. If the blood lead level appears high, you may want to wait until your blood lead level drops before attempting to conceive. You can talk to your doctor and union about strategies for reducing or eliminating your lead exposure to help get the blood lead exposure to drop.
Your occupational medicine physician may also want to check your blood lead levels during pregnancy, though currently there is no generally agreed upon treatment to reduce your lead level once you are pregnant.
What are Fetal Protection Policies?
Fetal protection policies are company policies that forbid fertile women from working in certain jobs, supposedly to protect the fetus. Such companies may not be necessarily interested in worker's health or fetal health, but may be more interested in protecting themselves from being sued. In Massachusetts, a recent survey showed that 20 % of the chemical and high tech companies have "fetal protection policies."
Some companies actually have barred all women from jobs that have lead exposure unless the woman brings a doctor's note proving she is not fertile. Some women felt that they had no other choice but to be sterilized in order to keep their jobs.
The Supreme Court has struck down these policies because they discriminate against women. The case was brought to the Supreme Court by the United Auto Workers against a lead battery manufacturer. The court ruled on March 21, 1991, that fetal protection policies violate The Pregnancy Disability Act of 1978 (an amendment to The Civil Rights Act). Justice Blackmun stated that "...women as capable of doing their jobs as their male counterparts may not be forced to choose between having a child and having a job." He also cited evidence that lead can have harmful effects on the male reproductive system as well.
What about OSHA?
OSHA's policies have not generally addressed the reproductive health of workers. In the OSHA lead standards for general industry and for construction, workers must be informed of the reproductive hazards of lead, and a doctor is allowed to medically remove a worker who is pregnant or who is planning to conceive a child. Unfortunately, OSHA does not cover public employees.
What Can We Do About Reproductive Hazards in the Workplace?
The answer is to get employers to clean up workplaces and keep exposures to lead and other substances as low as possible to protect both men and women. Improved contract specifications and OSHA regulations can help reduce our exposure to lead.
How Big of a Problem is Lead Poisoning in Adults?
No one knows for sure. What we do know is that workers whose jobs involve lead exposure are at risk of being lead poisoned. It is estimated that there are more than 1 million workers in over 100 different occupations that may be exposed to lead.
In some states there are lead registries to keep track of the number of workers who have blood lead levels above certain levels, usually around 25 ug/dl. In Massachusetts, the Lead Registry recorded over 300 workers with blood leads over 40 ug/dl in a 2-yr. period. Almost 2/3 of these workers were employed in construction.
What Jobs Have a Lead Hazard?
There are many jobs that expose workers to lead. Some examples are:
• Firing range employees
• Radiator repair workers
• Workers in lead smelters
• Lead miners
• Steel welders or cutters
• Industrial and construction painters
How Do We Prevent Lead Poisoning?
One of the most important public health measures our country has ever taken was to drastically reduce the amount of organic lead allowed in gasoline. (Sadly enough the Environmental Protection Agency initially took this action to protect pollution control devices in cars, not in children.) As a result, less lead is released into the atmosphere and also less was deposited in dust and soil. The nation's blood lead levels dropped an average of 37%.
Has the Lead in Paint Been Replaced by Safer Alternatives?
By the early years of this century, the paint manufactures had found other pigment substitutes for lead in paint. In the 1930's, white lead began to be replaced by titanium dioxide and zinc oxide. While in 1955 the paint industry had set a voluntary standard for itself of 1% lead in interior paints, this was not always followed. As late as 1971, more that 10% of the paints tested in New York City had between 2% -11% lead content. In 1973, the federal government finally limited the amount of lead in interior pant to .5% and, in 1978, this limit was lowered to .06%.
The story for industrial paint is different. Lead is still allowed in paint for bridge construction and machinery. It is used for its ability to expand and contract with the metal surface of a structure without cracking. It is also able to resist corrosion. Unfortunately, this paint is a significant source of lead exposure. Even if its use were banned today, there would still be exposure to workers and surrounding communities for years to come due to the number of metal structures, such as bridges, that are coated with it.
As recently as August 1990, the Shepard bridge in Lynn, Massachusetts, was sandblasted before being repainted. Neither the contractor nor the bridge's owner, the MBTA, tested to see if the bridge had lead paint. Unfortunately, 11 families with 15 children had to be relocated because their properties became contaminated with lead dust.
Material for this fact sheet was adapted from the "Lead Abatement Manual" of the Massachusetts Respiratory Hospital. This document was produced with funds provided by the Massachusetts Dept. of Industrial Accidents, Office for Safety.
This material was also adapted from "Lead in the Workplace, A Guide for Employers and Health & Safety Trainers" (California Department of Health Services)