Health monitoring: Lead (inorganic)

Occupational exposure to inorganic lead occurs in a wide range of industrial, manufacturing, construction and mining activities which produce lead dust or fumes.

Lead is present in significant quantities as a contaminant in the processing and smelting of mineral ores and hence in mining wastes.  Lead is used as an additive in fire assay laboratories and gold processing.  Inorganic lead itself is mined as lead sulphide (galena) or lead carbonate resulting in exposures from mining, processing, transportation and storage.  

Lead was historically used in fuel and paint, resulting in environmental contamination of soil.  It is present in solder, metal alloys, radiators, old paintwork, detonators, explosives, bullets, batteries and lead shielding from radiation. 

Lead-risk industries include lead soldering, radiator repair, lead alloys, fire assay laboratories, foundries (melting, casting, machining), lead battery manufacture or its breaking and dismantling, the welding, cutting or cleaning surfaces coated with lead or paint containing more than 1% lead, and its removal by abrasive blasting and high pressure water jet or machining.

Non-occupational exposure can be significant from activities such as melting lead sinkers (fishing), home renovations, lead paint removal, lead-lighting hobbies, use of cosmetics (kohl),  lead glazed food containers and glassware.

Inorganic lead enters the body through inhalation and ingestion. About 10% of ingested lead is absorbed in the gut. Between 50-80% of inhaled lead is absorbed through the lungs. Lead is excreted predominantly by the kidneys (70%).

Lead is distributed in three compartments in the body:

1. blood (binds quickly to red blood cells) with a half-life of 30-40 days
2. soft tissues (kidneys, brain, liver, bone marrow) with a half-life of 40 days, and
3. bone with a half-life of up to 25 years.

Ninety per cent of the total body lead is stored in bone. Lead is released from bone in osteoporosis and pregnancy and fractures will also raise the level of lead in blood.

Lead inhibits enzymes (including ALA dehydratase and ferrochelatase) which are involved in the synthesis of haem, an essential component of haemoglobin in red blood cells. Lead shortens the lifespan of red blood cells. Anaemia develops when the lifespan has been reduced from 120 days to 30 days. Affected red cells are more fragile and their removal from circulation stimulates bone marrow production resulting in stippled red cells.

Lead crosses the blood-brain barrier and placenta. Lead can be transferred from the mother to the infant through breast milk.

Lead is a cumulative toxic substance.  

In adults with chronic low level exposure, there may be effects on the body’s digestive, cardiovascular, renal, reproductive and neurological functions.  Chronic exposure to levels above 20 µg/dL can cause subclinical effects on cognitive function and adverse effects on sperm  quality. However, symptoms may be absent or mild until blood levels are significantly elevated.  Mood changes, anaemia, abdominal colic and constipation may be more apparent when blood lead levels exceed 60 µg/dL.

Exposure to high levels of lead dust or fumes cause anaemia, peripheral neuropathy, and damage to kidney and brain (encephalopathy).  However, severe health effects are now extremely rare in Australia.

Young children (under five years) are more vulnerable.  They absorb 3 times more lead than adults from ingestion.  They are more prone to encephalopathy at a lower blood lead level as their brains are rapidly developing.  Blood lead levels greater than 10 µg/dL may potentially be harmful with reports of impact on IQ, and behavioural disturbance. Ingested lead is absorbed at a higher rate in children. Hence, personal hygiene of the worker is vital to avoid contamination of the home environment.

Non-occuptional exposure levels

The average background blood lead level among Australians is less than 5 µg/dL (NHMRC, 2015; NHMRC, 2016). Levels above 5 µg/dL are considered to be consistent with exposure above the background level e.g. from work activities, hobbies or home renovations.

Baseline health monitoring is required prior to commencement of lead risk work, then at one month after the worker commences work. Thereafter, the frequency of testing is determined by the blood lead levels as outlined in the tables below.

Important considerations in the assessment of risk and the potential for elevated blood lead levels are:

• nature and duration of the exposure, including the year of first exposure
• work environment controls
• personal hygiene
• smoking history
• age and gender, specifically females of reproductive age.

Monitoring blood lead levels enables early intervention by the medical practitioner. Early intervention includes:

• education (lead hazard and health effects)
• counselling (safe work practices, personal hygiene)
• temporary removal from lead work
• re-instatement when appropriate
• feedback to the employer for remedial measures (to improve safety controls).

Workplaces should provide amenities for hot water for hand washing and showering. Personal hygiene must be strictly monitored (washing face and hands before eating; no smoking, eating or drinking in lead work area; laundry provisions, showering and changing into clean clothes before leaving work). It is essential that workers do not bring lead dust home from work.

The removal level of females of reproductive capacity is 10 µg/dL.

The removal level for males and females (not of reproductive capacity) is 30 µg/dL.

Pregnant and breast-feeding women should be removed from lead-risk work.

The registered medical practitioner has an important role in educating and reinforcing good personal hygiene and safe work practices through the following:

• Inform workers of potential adverse health effects from lead exposure to themselves and their family.
• Counsel all workers to stop smoking.
• Advise workers to be clean shaven to permit effective respiratory protection.
• Reinforce safe work practices (such as effective local exhaust ventilation, avoidance of dry sweeping, cleaning of the work area with HEPA filter vacuum cleaner, use of respirators with appropriate level of protection.).
• Reinforce personal hygiene and cleanliness, including:
  • washing face and hands before eating or drinking
  • avoiding eating, drinking or smoking in the workshop
  • showering and changing into clean clothes and footwear before leaving work.

The registered medical practitioner removes the worker from lead-risk work when the removal threshold is exceeded or when the blood lead level is close to approaching the removal threshold.

The registered medical practitioner arranges the removal of the worker from lead work immediately by notifying the regulator, PCBU and worker, and arranges a medical examination of the employee within seven days of the removal.

The frequency of blood lead level testing is at the discretion of the registered medical practitioner. The worker must not return to lead work until:

• the blood lead level is less than 20 µg/dL for male workers and female workers not of reproductive capacity, or
• the blood lead level is less than 5 µg/dL for female workers of reproductive capacity

and

• has been certified as suitable to return to lead work by the RMP.

The registered medical practitioner with relevant experience in health monitoring:

• supervises the health monitoring
• informs the worker and explains the results of the assessment
• informs the PCBU of the outcome of the assessment and advises on the need for remedial action (if any).

The registered medical practitioner (RMP) has a duty to notify health monitoring results to the regulator. The RMP forwards the completed Health Monitoring Notification Form- Lead along with the pathology laboratory report, to safety@demirs.wa.gov.au.