Inorganic lead is a malleable, blue-gray, heavy metal that occurs naturally in the Earth’s crust. Lead was one of the first metals used by humans and, consequently, the cause of the first recorded occupational disease (lead colic in a 4th century BC metal worker).
Lead was used extensively as a corrosion inhibitor and pigment in paints, but concerns over its toxicity led to the ban of the use of lead in paint for residential and public buildings.
Lead enters the body primarily through inhalation and ingestion, and passes through the lungs into the blood where it can harm many of the body's organ systems. While inorganic lead does not readily enter the body through the skin, it can enter the body through accidental ingestion (eating, drinking, and smoking) via contaminated hands, clothing, and surfaces.
Lead poisoning may occur in workers during abrasive blasting, sanding, cutting, burning, or welding of bridges and other steel structures such as water and fuel storage tanks coated with lead-containing paints. Workers who may be exposed to lead include abrasive blasters, inspectors, iron workers (welders and cutters), painters, and laborers.
Action level: The action level is the degree of employee exposure, without regard to the use of respirators, to an airborne concentration of lead of 30 micrograms per cubic meter of air (30 ug/m3) calculated as an 8-hour time-weighted average (TWA). Employers must determine if their employees performing manual demolition may be exposed to lead at or above the action level.
Permissible exposure limit (PEL): Employers must make sure that employees are not exposed to lead at concentrations greater than fifty micrograms per cubic meter of air (50 ug/m3) averaged over an 8-hour period.
If employees are exposed to lead for more than 8 hours in any work day, the permissible exposure limit, as a time weighted average (TWA) for that day, must be reduced according to the following formula:
Maximum permissible limit (in ug/m3) = 400 divided by hours worked in the day.
The frequency and severity of medical symptoms increase with the concentration of lead in the blood. Workers with blood lead levels (BLLs) of 80 µg/dl (micrograms/deciliter) or greater have symptoms or signs of acute lead poisoning, although in some individuals, symptoms may be so mild that they are overlooked.
Common symptoms of acute lead poisoning are loss of appetite, nausea, vomiting, stomach cramps, constipation, difficulty in sleeping, fatigue, moodiness, headache, joint or muscle aches, anemia, and decreased sexual drive.
Severe health effects of acute lead exposure include damage to the nervous system, including wrist or foot drop, tremors, and convulsions or seizures. Acute lead poisoning from uncontrolled occupational exposures has resulted in fatalities.
Chronic lead poisoning may result after lead has accumulated in the body over time, mostly in the bone. Long after exposure has ceased, some physiological event such as illness or pregnancy may release this stored lead from the bone and produce adverse health effects such as impaired hemoglobin synthesis, alteration in the central and peripheral nervous systems, hypertension, effects on male and female reproductive systems, and damage to the developing fetus. These health effects may occur at BLLs below 50 µg/dl.
Personal hygiene is an important element of any program for protecting workers from exposure to lead dust. OSHA requires employers to provide adequate washing facilities at the worksite so that workers can remove lead particles that accumulate on the skin and hair. Showers should also be available.
Effective source control measures (such as containment or local exhaust ventilation) should be implemented to minimize worker exposure to lead. NIOSH prefers such measures as the primary means of protecting workers, but source control at construction sites is often ineffective, and airborne lead concentrations may be high or may vary unpredictably.
Respiratory protection is also necessary for certain operations such as blasting, sweeping, vacuuming, and for other jobs as determined at the worksite by an industrial hygienist or other qualified professional. However, respirators are the least preferred method of controlling lead exposure, and they should not be used as the only means of preventing or minimizing exposures. The use of respirators should supplement the continued use of engineering controls and good work practices.
When respirators are used, the employer must establish a comprehensive respiratory protection program. Important elements of the OSHA respiratory protection standard are:
The program should be evaluated regularly by the employer. Without a complete respiratory protection program, workers will not receive the protection anticipated.
Respirators should be selected by the person who is in charge of the program and knowledgeable about the workplace and the limitations associated with each type of respirator. Because exposures to lead during construction may vary substantially throughout a workshift and between days, the highest anticipated exposure should be used to determine the appropriate respirator for each job.
Workers should receive training that includes the following:
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