Revised August, 2001
Lead is an element which has been used in many forms over a number of centuries. Lead was used in pottery glazes by the early Egyptians and in water pipes by the early Romans. Cases of lead poisoning were recorded as early as the eighteenth century in England where it was known as Devonshire Colic.
Lead is still widely used in modern industry and is present quite extensively in our environment. The purpose of this document is to provide information about the effects of lead exposure on the health of Nova Scotian workers and how to evaluate and control lead exposures.
Lead compounds are divided into two categories, organic and inorganic.
Organic compounds include most compounds containing lead and carbon at one time. The most well known organic lead compounds are tetraethyl and triethyl lead, which were once used as octane enhancers in gasoline. Today, organic lead compounds are used much less often - usually as drying agents for lacquers and similar materials.
Inorganic compounds include metallic lead, lead alloys, lead oxide, and lead sulphate. A major use of inorganic lead in Nova Scotia is in the manufacture of storage batteries. Lead can also be found in industrial paints (e.g., red lead oxide primer) or for use in assaying, soldering, radiator repair and metal reclaiming. Lead compounds are also used in jewellery making, stained glass making and in ceramic glazes.
This booklet deals solely with inorganic lead.
Since lead is widely present in the environment, everyone will have some detectable level of lead in their body. Usually the level is low and the person experiences no symptoms. However, individuals who are exposed to lead at work may be taking in more lead than the body can handle. The resulting lead levels may produce negative health effects.
Inorganic lead can be taken into the body through ingestion or inhalation of dust or fumes. Ingestion of lead can occur without the individual knowing that their food, drink or cigarette has become contaminated. Inorganic lead cannot be absorbed through unbroken skin.
Once inorganic lead compounds are absorbed into the body, negative health effects may occur. Body organs and systems, including the blood, kidneys, central nervous system and digestive system, can be affected. Common symptoms of long term lead poisoning include anaemia, loss of appetite, fatigue and constipation. If lead continues to build up in the body, progressively more serious effects can occur, including permanent nerve damage and, in the extreme case, death.
Short term but very high lead exposures are quite rare in industry, but have been observed in children exposed to lead through eating paint or some other compound containing lead. Severe effects include nausea, vomiting, kidney damage and, in the extreme case, death.
Everyone will have a small amount of lead in their body. Therefore, there must be a way of determining the extent of lead exposure. In workplaces where lead is used and exposures are often the highest, this is usually done by assessing environmental factors, such as air concentrations of lead; biological factors, such as blood concentrations of lead; or a combination of these factors.
The following sections will discuss in greater detail how the evaluation can be made.
Inorganic lead can enter the air in the form of dust, fumes or vapours. The form of the lead material will influence the evaluation of exposure and the control measures that can be used to prevent further exposure.
When air sampling is performed, it is recommended that a sampling method approved by the National Institute for Occupational Safety and Health (a branch of the United States Department of Health and Human Services) be used.
In general, sampling involves drawing a known amount of air through a filter and analyzing the filter to determine the lead content. The sample may be collected as a personal sample (from the breathing zone of the worker) or as an area sample, depending on the type of information needed.
Samples should be collected to represent the work activities. Therefore, if activities vary over the day, an eight hour (or longer) sample may be required. Where activities, and thus lead exposures, remain relatively constant over the work day, a shorter sampling period may be satisfactory.
The air sampling results are calculated in terms of the quantity of lead in micrograms per cubic meter of air (micrograms/m3). These values are compared to an exposure standard to determine if personnel are at risk of adverse health effects due to lead exposures.
|Inorganic Lead (as dust or fume)||50 micrograms/m3 (as lead)|
|Lead chromate||50 micrograms/m3 (as chromium)|
|Lead arsenate||150 micrograms/m3 (as lead arsenate)|
Where these standards are exceeded in a workplace, it is necessary to reduce personnel exposure through appropriate control measures.
Lead must be absorbed into the body before there is a health risk. When lead is absorbed, it can be measured in blood and urine. The amount of lead in blood is the most commonly used indicator of exposure to inorganic lead. Blood lead levels do not fluctuate as much as urinary lead levels.
As with air sampling, proper sampling methods must be followed when determining an individual's blood lead level. The recommended methods for biological monitoring should be reviewed with an appropriate health professional.
A person who has no occupational exposure to lead will generally have a blood lead level of less than 1.5 micromoles of lead per litre of blood (micromoles/L). In general, people who live in urban areas have higher blood lead levels than people who live in rural areas.
Blood lead levels of more than 1.5 micromoles/L indicate elevated lead absorption. Persons showing a blood lead level higher than this may experience adverse health effects. Depending on the measured blood lead level, it may be necessary for the physician to perform clinical tests to diagnose the effects of lead exposure.
It should be noted that lead may affect fertility in both men and women and may produce developmental problems in the unborn child. Therefore, it is recommended that men and women who are planning to have a child maintain a blood lead level below 1.5 micromoles/L.
If an evaluation of lead exposures reveals that personnel are overexposed to lead, control measures will be required. Control measures can include a variety of different methods to reduce exposures. Factors such as the route of exposure, the physical form of the lead and the duration of exposure will affect the selection of a control measure. The following section describes in greater detail the different control measures available and where a particular measure would be appropriate.
The term "engineering controls" is usually used to describe control measures which do not specifically rely on worker participation to reduce exposures. For example, a change from a manual loading process to an automatic feed system or the use of a ventilation system to capture lead at the source would reduce worker exposure in the lead handling processes.
For the control of lead compounds, local exhaust ventilation may be required to reduce exposures. Ideally, the exhaust ventilation system will include a hood which encloses the process. Alternatively, a hood may be located as close to the process as possible to draw the lead material away from the employee. The required air velocity of the system will depend on the process being controlled.
Air from a lead exhaust system should be treated to prevent the release of lead into the atmosphere. The type of treatment required will depend of the form and the amount of lead contamination. For example, cyclones or baghouse filters may be adequate to remove coarse dust but may not be suitable to remove very small particles of lead fume. Further information is available from filtration equipment manufacturers.
Ventilation control measures are usually best suited to a fixed process where the operator remains at a work station and the exposure remains relatively constant over the work day. Where ventilation control is used, proper engineering design principles should be followed. It may be necessary to consult an engineer with experience in the field of ventilation design.
Depending on the type of exposure, personal protective equipment may be required to reduce exposures to lead. The effectiveness of personal protective equipment depends on the co-operation of the user. It is extremely important to have a program which highlights the importance and reasons for use, as well as training in the proper use and maintenance of the equipment.
There are some conditions where respirators may be used to protect an individual from lead exposure. For example, respirators may be used in emergency conditions where control equipment has broken down, where high exposure cannot be controlled by other means, and during some maintenance activities.
A number of different respirators are available to provide protection from lead exposure. An evaluation of exposures is required to determine the appropriate respirator.
An approved respirator is one which has been certified and labelled as suitable for the specific exposure conditions by a recognized agency, such as the National Institute for Occupational Safety and Health (NIOSH). It may be necessary to consult an individual with experience in respirator selection to identify the appropriate respirator.
Half facepiece respirators must be properly fitted and used with the appropriate cartridge. This type of respirator is only acceptable for use as protection against inorganic lead dust. A properly fitted half facepiece respirator equipped with High Efficiency Particulate Air (HEPA) filters can provide protection against inorganic lead dust or fume up to ten times the legal limit (500 micrograms/m3).
Full facepiece, air-purifying respirators with appropriate filters give a better level of protection. A properly fitted full facepiece respirator can provide protection against inorganic lead dust or fume up to fifty times the legal limit (2500 micrograms/m3).
Powered air-purifying respirators fitted with the correct filters provide the next level of protection. These respirators have a battery-operated fan which drives the air through the filter and then into the facepiece. The respirators produce a positive pressure which causes air to leak out of the facepiece rather than in. This helps prevent contaminated air from entering the breathing zone. When fitted with proper filters, these respirators can provide protection against inorganic lead dust or fume up to 1000 times the legal limit (50 000 micrograms/m3).
For protection against exposure to even higher concentrations of inorganic lead dust or fume (up to 100 000 micrograms/m3), a supplied air respirator with a full facepiece and operated in a positive pressure mode is required.
For extremely high concentrations (greater than 100 000 micrograms/m3), firefighting, or where the concentration is unknown, a full facepiece, self-contained breathing apparatus operated in positive-pressure mode must be used.
Any respirator program will involve these crucial elements:
1. Selection of the appropriate respirator and filter for the circumstances.
2. Proper fitting of the respirator. This includes ensuring that there is a satisfactory seal between the respirator and the face. The presence of facial hair will greatly reduce the efficiency of the respirator. Therefore, all personnel required to wear respirators should be clean shaven where the seal meets the skin. Consult the CSA Standard Z94.4-93 "Selection, Use, and Care of Respirators" for more information.
3. Instruction as to correct use, storage, and maintenance of the respirator.
4. Education as to why the respirator is required and the possible health effects which may occur if it is not used properly.
Depending on the process, other personal protective equipment may be required to minimize lead exposures. It may be appropriate to wear protective clothing (coveralls) over or instead of personal clothing to prevent the contamination of personal effects with lead.
Where the work requires protective clothing, appropriate changing facilities should be provided. Contaminated and uncontaminated clothing should be stored in separate areas at the worksite to prevent the clean clothing from becoming contaminated.
Arrangements should be made to have the contaminated clothing laundered in a manner which will not unnecessarily expose the laundry personnel to lead. Usually this involves sealing the clothing in impermeable plastic bags to be sent to the laundry. Once there, the bags are submerged in water, and opened to allow the clothing to become water saturated.
Where workers are exposed to lead-containing materials a program of health monitoring is recommended. The specifics of such a program are identified in the Code of Practice for Working with Lead, available from the Department of Labour and Advanced Education. As part of the program, workers who have blood lead levels in excess of the established criteria or who exhibit symptoms must be removed from exposure.
Since lead is widely present in the environment, criteria should be established to define what airborne lead concentration will be considered "removal from lead exposure". The Department of Environment and Labour recommends that lead-free areas be defined as those with airborne lead levels less than 10 micrograms/m3, measured as elemental lead.
To prevent the accidental intake of lead compounds, personal hygiene is very important for lead workers. If food, drink, or cigarettes are stored in a lead contaminated area, they may become contaminated. When they are consumed, lead can be taken directly into the body. The same is true if the hands are not free of lead prior to eating, drinking or smoking. Therefore, it is extremely important to eat, drink or smoke in an uncontaminated area after thoroughly cleaning the hands and face.
Depending on the level of contamination, it may be necessary for personnel to shower before leaving the work site, or at the end of a work shift. Lead dust which is on the hair or on the body can be resuspended in air and then inhaled by the employee or possibly a family member.
Personal hygiene must be taught and reinforced with a health education program and adequate facilities.
Where lead dust is present in an area, good housekeeping can be very important in minimizing lead exposures.
Dry sweeping or the use of compressed air to clean a lead contaminated area can create a serious problem, as fine dry dust becomes suspended in air where it can easily be inhaled by personnel. Dust can also become suspended in air if a regular vacuum cleaner is used to clean an area.
Only a vacuum with high efficiency (HEPA) filters or a system which is exhausted directly outside is recommended for cleaning lead contaminated areas. An alternative to this equipment is the use of wet cleaning methods.
The object in every workplace should be to reduce lead exposure to the lowest possible level.
A combination of good health education and adequate control measures will help to minimize risks. Lead control programs must be planned in conjunction with the Joint Occupational Health and Safety Committee or Health and Safety Representative, where they exist.
It is also necessary to periodically review the program to ensure changes to work processes have not altered the lead exposures. Periodic review and evaluation is important in determining whether the most up-to-date and appropriate control methods are being used.