Should we test fresh produce for lead?

In July 2011, Food Standards Australia and New Zealand (FSANZ) published Maximum Levels (MLs) for lead in the Food Standards Code.  After this major retailers began asking suppliers to test fresh fruit and vegetables to prove that levels complied with MLs.

Lead is a toxin that affects the blood, nervous system and kidneys.  High concentrations of lead may result in anaemia, hyperactive behaviour, mental retardation, seizures or cerebral palsy.  Lead may accumulate in the kidneys causing irreversible damage.  Infants and children are more vulnerable to lead exposure because they consume more food relative to body weight.

Diet is a significant part of exposure to lead, but much of the risk comes from processed foods especially if solder is used to secure the seams of cans.  Infants and children may ingest lead as paint, soil or dust.

The FSANZ MLs are based on dietary studies and a tolerable weekly intake of 25 micrograms of lead per kilogram of body weight.  The amount of each food type consumed is considered along with the levels that are achievable with sound production practices.

MLs for fresh produce are compared to those for other foods in the following table.

Type of Food ML for lead
Shellfish 2.0
Fish.  Edible offal of cattle, sheep, pig and poultry 0.5
Brassicas 0.3
Cereals, pulses and legumes 0.2
Vegetables (except brassicas) and fruit 0.1
Meat of cattle, sheep, pig and poultry (excluding offal) 0.1
Infant formulae 0.02

Lead concentrations are low in farming environments and produce is unlikely to have unacceptable levels of lead unless the site is contaminated.  This may result from fumes from nearby heavy vehicle traffic, dumping of old paint or weathering of paint from buildings, and from previous use for storage or discharging of firearms (e.g. rifle range). Lead can also be of concern if growing sites are located near a smelter.

Supermarket quality assurance departments are prepared to exempt suppliers from testing produce for lead testing if the supplier can demonstrate by risk assessment that testing is unnecessary.  The risk assessment needs to consider the possibility of site contamination and the chance that inputs may contain lead.  In general, farming systems do not use inputs that contain more than trace amounts of this metal.

The risk assessment should be backed up by a body of test results that verify that lead levels are consistently under the maximum level.

Since September 2010 Rudge Produce Systems and Total Quality Assurance Services have conducted lead tests on more than 1500 samples of fresh produce.  These tests covered a wide range of fruits and vegetables and in ninety percent of samples there was no lead above the detection level of 0.005ppm.

There were two samples (avocado and potato) were lead levels were over the ML and in a small percentage of samples of leafy vegetables and root vegetables we detected levels that were more than half of the ML.  This data indicates that there may be instances where environmental factors or crop inputs expose produce to lead.

Growers also need to consider inputs that may contain lead, these include copper fungicides.  In many types of produce multiple applications of copper fungicides are used to protect crops from fungal and bacterial diseases.  As part of the risk assessment growers should use only products where manufacturers can provide evidence that lead concentrations are within the international standard (250 parts per million).

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