Pure lead (Pb) is a heavy metal at room temperature and pressure and is a basic chemical element. It can combine with various other substances to form numerous lead compounds. The word "lead" as used in the OSHA standard refers to elemental lead, all inorganic lead compounds and a class of organic lead compounds called lead soaps. The standard does not apply to other organic lead compounds.
Exposure to lead occurs in several different occupations in the construction industry, including demolition of structures where lead is present, removal or encapsulation of lead containing materials, new construction, alteration, repair, or renovation of structures that contain lead, and installation of products containing lead. In addition, there are construction related activities where exposure to lead may occur, including transportation, disposal, storage, or containment of lead on construction sites, and maintenance operations associated with construction activities.
Permissible Exposure- The permissible exposure limit (PEL) set by the OSHA standard is 50 micrograms of lead per cubic meter of air, averaged over an 8-hour workday.
Action Level- The OSHA standard establishes an action level of 30 micrograms of lead per cubic meter of air, averaged over an 8-hour workday. The action level triggers several provisions of the standard such as exposure monitoring, medical surveillance, and training.
When absorbed into the body in certain doses, lead is a toxic substance. The object of the lead standard is to prevent absorption of harmful quantities of lead. The standard is intended to protect employees from the immediate toxic effects of lead and the serious toxic effects that may not become apparent until years of exposure have passed. Lead can be absorbed into the body by inhalation (breathing) and ingestion (eating). Lead (except for certain organic lead compounds not covered by the standard, such as tetraethyl lead) is not absorbed through the skin. When lead is scattered in the air as a dust, fume, or mist it can be inhaled and absorbed through the lungs and upper respiratory tract. Inhalation of airborne lead is generally the most important source of occupational lead absorption. Lead can be absorbed through the digestive system if lead gets into the mouth and is swallowed. If food, cigarettes, chewing tobacco, or make-up is handled which has lead on them or your hands are contaminated with lead, this will contribute to ingestion.
A significant portion of lead that is inhaled or ingested gets into the blood stream. Once in the blood stream, lead is circulated throughout the body and stored in various organs and body tissues. Some of this lead is quickly filtered out of the body and excreted, but some remains in the blood and other tissues. As exposure to lead continues, the amount stored in the body will increase if more lead is absorbed than your body excretes. Even though you may not be aware of any immediate symptoms of disease, lead stored in your tissues can slowly cause irreversible damage, first to individual cells, then to your organs and whole body systems.
Effects of overexposure to lead
Short term (acute) overexposure
Lead is a potent poison that serves no useful function in the body. Taken in large enough doses, lead can kill in a matter of days. A condition affecting the brain may arise which develops quickly to seizures, coma, and death. Short term occupational exposures of this magnitude are highly unusual, but possible. Similar forms of brain damage may arise from chronic exposure to lower doses of lead. There is no sharp dividing line between rapidly developing acute effects of lead, and chronic effects which take longer to acquire. Lead affects numerous body systems, and causes health impairment and disease after periods of exposure as short as days or as long as several years.
Long term (chronic) overexposure
Chronic overexposure to lead may result in severe damage to your blood - forming, nervous, urinary and reproductive systems. Some common symptoms of chronic exposure include loss of appetite, metallic taste in the mouth, anxiety, constipation, nausea, pallor, tiredness, weakness, insomnia, headache, nervous irritability, muscle and joint pain or soreness, fine tremors, numbness, dizziness, hyperactivity, and abdominal pain.
Damage to the central nervous system and the brain is one of the most severe forms of lead poisoning. The most severe, often fatal, form of brain damage may be preceded by vomiting, a feeling of dullness progressing to drowsiness and stupor, poor memory, restlessness, irritability, tremor, and convulsions. It may arise suddenly with the onset of seizures, followed by coma, and death. Muscular weakness may also develop. This weakness may progress to paralysis often observed as a characteristic "wrist drop" or "foot drop".
Chronic overexposure to lead also results in kidney disease with few, if any, symptoms appearing until extensive and permanent kidney damage has occurred. Laboratory tests reveal the presence of this kidney disease only after about two-thirds of kidney function is lost. When symptoms of urinary dysfunction arise, it is often too late to correct or prevent worsening conditions, and progression to kidney dialysis or death is possible.
Chronic overexposure to lead impairs the reproductive systems of both men and women. Overexposure to lead may result in decreased sex drive, impotence and sterility in men. Lead can alter the structure of sperm cells raising the risk of birth defects. There is evidence of miscarriage and stillbirth in women whose husbands were exposed to lead or who were exposed to lead themselves. Lead exposure also may result in decreased fertility, and abnormal menstrual cycles in women. The course of pregnancy may be adversely affected by exposure to lead since lead crosses the placental barrier and poses risks to developing fetuses. Children born of parents exposed to excess lead levels are more likely to have birth defects, mental retardation, behavioral disorders or die during the first year of childhood.
Overexposure to lead also disrupts the blood - forming system resulting in decreased hemoglobin (the substance in the blood that carries oxygen to the cells) and ultimately anemia. Anemia is characterized by weakness, pallor and fatigability as a result of decreased oxygen carrying capacity in the blood.
Health protection goals of the standard
Prevention of health effects for workers from exposure to lead throughout a working lifetime requires that the blood lead level (BLL) be maintained below forty micrograms per deciliter of whole blood (40 ug/dl). The blood lead levels of male and female workers who intend to have children should be maintained below 30 ug/dl to minimize reproductive health effects to the parents and to the developing fetus. The measurement of BLL is the most useful indicator of the amount of lead being absorbed by the body.
BLL measurements show the amount of lead circulating in the blood, but do not give any information about the amount of lead stored in tissues. BLL measurements show current absorption of lead, not the effect that lead is having on the body or the effects that past lead exposure may have already caused. Research into lead related diseases has focused on associations between BLLs and various diseases. BLL is an important indicator of the likelihood that a worker will gradually acquire a lead related health impairment or disease. Once the blood lead level climbs above 40 ug/dl, the risk of disease increases. There is a wide variability of individual response to lead, thus it is difficult to say that a particular BLL in a given person will cause a particular effect. Studies have associated fatal brain damage with BLLs as low as 150 ug/dl. Other studies have shown other forms of diseases in some workers with BLLs well below 80 ug/dl. BLL is a crucial indicator of the risks to a worker=s health, but one other factor is also extremely important. This factor is the length of time the BLLs have been elevated. The longer the BLL is elevated, the greater the risk that lead is being gradually stored in the organs and tissues (body burden). The greater the body burden, the greater the chances of permanent damage. The best way to prevent all forms of lead related impairments and diseases is to maintain the BLL below 40 ug/dl. The provisions of the standard are designed with this end in mind.
Employers have the prime responsibility to assure that the provisions of the standard are complied with both by the company and by individual workers. Workers, however, also have a responsibility to assist employers in complying with the standard. Workers can play a key role in protecting their own health by learning about hazards and control strategies, learning what the standard requires, and following the requirements of the standard.
Reporting signs and symptoms of health problems
Immediately notify your employer if you develop signs or symptoms associated with lead poisoning or if you desire medical advice concerning the effects of current or past exposure to lead or your ability to have a healthy child. Notify your employer if you have difficulty breathing during a respirator fit test or while wearing a respirator. In each of these cases, the employer will make available to you appropriate medical examinations or consultations. These must be provided at no cost to you and at a reasonable time and place. The standard contains a procedure whereby you can obtain a second opinion by a physician of your choice if your employer selected the initial physician.
Source: OSHA Lead Standard