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Publication Number: FHWA-RD-98-179
Bridge Lead Removal and General Site Safety
Health Effects Caused By Lead Exposure
Table of Contents
Lead has been shown to cause a wide variety of health effects. Many of the effects have been known since ancient times, although some of the more subtle effects have been discovered only recently
It is important to understand the ways that lead can get into the body. This is referred to as routes of exposure. With lead, there are two main routes of exposure: inhalation and ingestion.
This is by far the most important exposure route in construction. Lead may be in the air if dust is created by grinding or similar procedures, or if fumes are created by welding torches. High levels of lead may be present yet not be visible to the naked eye. This airborne material is easily breathed in by any workers in the vicinity. Once inhaled, air follows a pathway from the nose to the windpipe, and then travels to the lungs.
Ingestion exposures can happen on the job in surprising ways. Many cases have been documented where workers consumed significant amounts of lead because they handled food and cigarettes before they washed the lead dust off their hands and clothes.
Ingestion also is a major problem for small children. Children sometimes swallow interior paint chips, which have a slightly sweet taste. Because of this problem, lead paint for use on interior surfaces and toys has been banned for many years.
Once in the bloodstream, lead goes with the blood to the kidney. The kidney's job is to purify the blood before it is distributed for use by the rest of the body. However, the kidney is not effective in removing lead, so much of the lead is carried by the bloodstream to other organs of the body, where some of it is stored. Lead can be stored in bones, in organs, such as the liver and kidney, and in fatty tissue. Lead can be stored in the bones for a long time. The total amount of lead stored in the body is called the "body burden." Lead stored in the body can be slowly released over time. This hazard is very significant for bridge workers. It means that the body can continue to be exposed to lead months or years after the original exposure.
Toxic effects are typically broken down into two categories: acute (short-term) effects and chronic (long-term) effects.
Acute effects show up relatively soon after serious exposure occurs. Excessive exposure to lead can result in a variety of symptoms, including a metallic taste, stomach pain and vomiting, diarrhea, and black stools. Severe exposure can cause nervous system damage, with symptoms such as intoxication, coma, respiratory arrest, and even death.
Chronic effects take some time before they begin to develop and often are attributed to low exposures (doses) adding up over a long period of time. The symptoms often seen with significant long-term exposure include loss of appetite, constipation, nausea, and stomach pain. Symptoms also can include excessive tiredness, weakness, weight loss, insomnia, headache, nervous irritability, fine tremors, numbness, dizziness, anxiety, and hyperactivity. Because these symptoms are common to a variety of health problems, they can be overlooked by exposed workers.
The following two blood tests are required to be performed on all workers who have, or are expected to have, exposures to lead greater than the Permissible Exposure Level (PEL) of 50 micrograms per cubic meter of air (50 µg/m³):
This test gives a picture of the amount of lead circulating in the blood. Lead can cause health damage at around 40 micrograms per deciliter of blood (µg/dl), although many workers will not experience symptoms at this level. At 40 µg/dI, children experience more symptoms than adults because of their smaller size. At levels of 60 µg/dl and up, symptoms begin to develop in most workers. Levels above 80 µg/dl are likely to cause serious lead poisoning. The OSHA PEL was established to keep blood lead levels below 40 µg/dl. The PEL is an average air concentration of some contaminant that cannot be exceeded during an 8-hour day.
The zinc protoporphyrin (ZPP) test also is used for lead testing. This test measures how much the blood-forming process has been interfered with by lead. The ZPP test looks at exposures, and their effects, that have occurred over the past 2 to 3 months. It is easy to perform, as it requires only a drop of blood from a pinprick. The analysis is done by a machine. ZPP levels greater than 50 are considered elevated.
Medical treatment of workers with lead poisoning involves removal from further exposure and sometimes involves administration of special drugs called chelating agents. Chelate is a Latin word for claw, and these drugs work by latching on to lead in the body. The chelating agent is then excreted from the body through the urine. However, the chelating agents also can latch onto other mineral nutrients, such as calcium and manganese, causing the person additional health problems. Consequently, chelating agents must be given under the strict supervision of a doctor.
Chelation is an important tool for ridding the body of excess lead. It does not protect or cure lead-inflicted damage to tissues. It does limit the lead available to cause such damage. Keep in mind that chelation is a last resort. Chelation is a very painful process. The OSHA lead construction standard prohibits the prophylactic use of chelating agents.