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Information sheet: lead in blood suspension level

In September 2010, the Department of Labour lowered the Suspension Level for lead in blood.  

The old suspension level for lead in blood (as of 2002) was:

The new suspension level for lead in blood (effective from September 2010) is:

The BEI for lead is 1.5µmol/L whole blood.

What is a suspension level?

A suspension level is used to suspend employees with high blood lead levels from working with lead until the lead in their bodies reduces to an acceptable level.

What is a Biological Exposure Index (BEI)?

A BEI is related to the Workplace Exposure Standard (WES) for the same substance.  If an employee’s inhalation exposure is equal to the WES, and he/she is engaged in moderate work, the BEI represents the expected level of the substance that would be present in the employee’s body.

In the case of lead, if an employee supplies a blood test result of 2.4µmol/litre whole blood or greater, this could indicate that the employee has been exposed to the inorganic lead dust WES of 0.1mg/m3 or higher.

Why did the Department of Labour change the suspension level for lead?

The lead in blood suspension level was lowered because current research shows that adverse health effects of lead can occur at concentrations lower than previously thought. 

Lowering the suspension level means more may have to be done in the workplace to reduce the level of employee exposure to this substance.

What are the health effects of lead exposure?

Lead is a poison that can accumulate (build up) in the body and it takes some time for the body to eliminate it.  The central nervous system (brain) is the most sensitive critical organ for lead absorption, and bone tissue stores about 90% of absorbed lead.

Lead poisoning in employees can cause abdominal pain, tiredness, aching limbs and joints, and irritability.  Nerve palsy and “wrist drop” can occur in severe cases. 

Lead can also be harmful to unborn babies as it can be absorbed from the mother through the placenta. 

What occupations are linked to lead exposure?

Lead is a bluish grey metal that occurs naturally in various mineral forms in the earth’s crust.  It has been widely used for hundreds of years because it is readily shaped and moulded, and is resistant to corrosion.

 “Organic” lead refers to lead compounds which contain carbon e.g. tetraethyl lead; and “inorganic lead” refers to compounds that do not contain carbon, including metallic lead, lead oxides and lead fume. 

The body absorbs organic lead (as was used in leaded petrol and still sometimes used in occupational settings) faster than it does inorganic lead. However the most significant airborne exposure today is from inorganic lead particulate matter.

Inorganic lead dust and fumes can be absorbed into the body by inhalation (breathing) and ingesting (eating, smoking or chewing fingernails). 

Lead is used in storage batteries, ammunition, cable sheaths, solder material, and the plastics industry.  It is also present in many metals, such as brass, some diving or fishing weights, pottery and stained-glass window manufacturing.

Lead was present in petrol, but since the introduction of unleaded petrol, this once significant form of exposure is no longer a concern.

Occupations with a high risk of exposure to lead include:

How is a BEI tested?

Lead in an employee’s body is detected by blood tests.  The tests are normally conducted every three months, but sometimes they may be conducted monthly for reasons such as an increased exposure to lead, or if a female worker is pregnant.

If an employee’s blood test result shows that the blood lead level is 2.4µmol/litre whole blood or greater, a Departmental Medical Practitioner from the Department of Labour can order the employee to be “suspended” from work (or from the work area where lead is present), until the employee’s follow-up tests indicate that their blood lead level has fallen to 1.93µmol/litre or below. 

It is preferable that employees’ blood lead levels should stay at or below 1.5µmol/litre whole blood. This does not include pregnant women or women planning on becoming pregnant soon, as they should be exposed to as little lead as possible. Ideally they should have no exposure at all as the developing foetus is extremely susceptible to lead. In addition, accumulated lead may be released from bones during times of calcium stress such as pregnancy and lactation.

The employer must provide the results of blood tests to the individual employees concerned.  It is important to ensure that employee privacy is preserved, and that no personal details are revealed to anyone without the employee’s permission.

What if the employee doesn’t want to have blood tests?

There are valid reasons why an employee may not want to have blood tests taken.  These reasons could be cultural, religious, or even a fear of needles or blood. 

Employees need to be informed by their employer that the reason why the tests are needed is to make sure that they are not being put at risk of becoming sick from too much exposure to lead. 

While any person can refuse to have a blood test, the employer must tell employees what the possible consequences could be if they refuse.  Consequences may include removal from the work area until tests are undertaken, a requirement for the employee to pay for the testing, and potentially others depending on the terms of the employment agreement.

The employer and employee should work together in good faith to resolve the issue to mutual benefit.

What can be done to lower the amount of hazardous substances in the workplace air?

There are a number of ways to lower hazardous substances in the air, but it depends on a number of things including the work process, the equipment used and the environment you work in.

Here are some general examples of what could be done to lower worker exposure to hazardous substances:

Why can’t we just rely on PPE to protect employees from harm?

The Health and Safety in Employment Act 1992 places duties on employers to eliminate all significant hazards in the workplace to ensure the safest working environment. 

But in a lot of cases, we need to work with certain machines, chemicals and hazardous processes in order to get the job done.  If the hazards cannot be eliminated, the employer is required to isolate the hazards from the workers, e.g. by installing machine guards, or by enclosing loud machinery in muffling equipment. 

Eliminating and isolating hazards can be initially expensive, and can take some time to develop.  But they are the preferred method of hazard management, and make good business sense.

If some hazards cannot be eliminated or isolated, the employer must minimise employee exposure.  Minimisation includes extraction ventilation, job rotation and using PPE. 

PPE may seem like the cheapest way to solve a hazardous substance exposure problem, but in most cases, it may end up costing the employer more money to manage it.  Since PPE doesn’t form a total barrier of protection for the worker, many things could happen. 

For example:

In your workplace, the principles for dealing with hazardous substance exposure must be to:

ELIMINATE, ISOLATE, MINIMISE.

Further sources of information:

Contact the Department of Labour on 0800 20 90 20 or visit www.dol.govt.nz.