Human Health Risk Assessment

At the request of the Minister for the Environment, the NSW Chief Scientist & Engineer commissioned an independent Human Health Risk Assessment (HHRA) for the Lord Howe Island’s proposed Rodent Eradication Program.

The HHRA looked at a number of potential exposure pathways – human interaction with the bait, including exposure through soil, air (dust), sediment, surface water, tank water as well as food sources such as seafood and locally grown fruits and vegetables.

Potential risks from these pathways were then considered for those most sensitive, which included toddlers, school children, pregnant women and adults spending large amounts of time outside.

A risk assessment of these exposure pathways and population groups concluded that:

Exposure to brodifacoum – from all potential sources – is below the NOEL and is not expected to result in adverse health effects.

The HHRA also assessed potential exposure due to ingestion of pellets and found that ingestion of one or a few pellets by a child is unlikely to result in any observable adverse effects.

Read the full Human Health Risk Assessment Presentation

Recommendation 1

That the Lord Howe Island Board note the Human Health Risk Assessment report and its advice that the proposed Rodent Eradication Program is not expected to result in adverse health effects for any individual due to exposure to brodifacoum.

Recommendation 2

Noting the considerable remaining community concern on Lord Howe Island, that the Minister request the Lord Howe Island Board to deliver:

  • A communication strategy for the period before and during the Rodent Eradication Program that clearly articulates the following: the reason for the eradication and approach chosen, guidance to residents and visitors on actions that they should and could take 
during the Rodent Eradication Program to minimise exposure to brodifacoum, and plans for follow-up measures that will be taken after the eradication program.
  • A monitoring strategy to measure the outcomes and impacts of the Rodent Eradication Program, including the potential re-emergence of rodents, as well as triggers that would lead to further action reports to the Minister following the Rodent Eradication Program on community and environmental outcomes, at designated time frames, such as one month after the second bait distribution, one month after re-introduction of birds and cattle, and two years post the Rodent Eradication Program.

What is a Human Health Risk Assessment?

HHRA is used to inform and assist decision-makers in managing chemical exposure issues with careful consideration of site-specific circumstances. It is used to estimate, in a way that is adequately protective of health, the potential for chemical exposures to represent a risk of adverse effects on the health of populations potentially exposed to it.

The risk assessment process usually involves:

Detailed Findings

Water (ground/surface/tank) (Section
Soil (soil/sand/sediment) (Section
Air (Section
Food (fruit/veges/seafood) (Section

The HHRA study found that exposure from all pathways combined are below those likely to result in adverse health effects.

What if I come into contact with the bait?

The below tables show details on sensitive groups and the expected effects of different pathways of contact with the bait.

Table 5: shows the overall ‘Hazard Index’ for each group.

How to read the table:

The hazard Index and hazard quotients are presented as a number:

  • zero – no exposure
  • one – exposure at the NOEL level
  • above one – exposure above the NOEL

Read more about the No Observable Effect Level (NOEL)

Ideally, hazard index and hazard quotients should be below one meaning that for each of the exposure pathways and all exposure pathways combined, exposure is below the NOEL and no adverse health effects are expected. (Read More)

As you can see by Table 4 & 5 the HHRA concluded that risk to the sensitive groups outlined was below NOEL and therefore no adverse health effects are expected.

As there is a potential, particularly for children, to ingest baits, the number of baits needed to result in an adverse effect was calculated for toddlers and schoolchildren (Table 6). Depending on the age group and pellet size, the number needed to be ingested to result in an adverse effect ranged from 5.6 to 44.5 over a period of up to two days.

10mm (Aerial broadcast pellet baits)
5.5mm (Hand broadcast pellet baits)

Table 5: Hazard Index for the different population groups

Population GroupHazard Index
School Child0.54
Pregnant Woman0.69

Table 4: Hazard Quotient estimates

Exposure PathwayToddlerSchool ChildPregnant FemaleAdult
Incidental soil ingestion0.20.0830.0270.023
Dermal contact with soil0.0940.0720.070.065
Inhalation of outdoor dust during aerial distribution0.0260.0650.10.1
Dermal contact with surface water0.0050.00360.00340.0033
Incidental ingestion of surface water2.8E-52.3E-53.1E-62.7E-6
Dermal contact with sediment0.140.110.000830.00076
Incidental ingestion of sediment0.00710.00290.00160.0014
Ingestion of fruit and vegetables0.0510.0210.0260.026
Ingestion of seafood0.0360.020.0190.016
Ingestion of tank water for potable purposes0.30.170.440.33

Table 6: Number of pellets need to result in an adverse effect

GroupNumber of 10 mm Pestoff 20R pelletsNumber of 5.5 mm Pestoff 20R pellets
School child18.844.5

Who conducted the study?

The HHRA was overseen by the NSW Chief Scientist and Engineer who established an Expert Panel. The Expert Panel and Lord Howe Island community members Rob Rathgeber and Frank Reed selected an independent company, Ramboll Environ to undertake the HHRA.

Company profile: Ramboll Environ

Profiles of Expert Panel assessment members:

Why was the study conducted?

In 2010, a HHRA was completed by Toxikos on behalf of the LHIB to evaluate human health concerns; however some concerns have continued to be expressed about potential human health impacts of the eradication program.

Therefore in addition to the Toxikos HHRA, there was requested a need for a fully independent HHRA to be completed with review by an external panel that had specialists in toxicology and public health.

Consequently, to address these human health concerns, the LHIB asked the OCSE to commission an additional HHRA with independent oversight of the process through an Expert Panel.

The OCSE undertook a procurement process as per the NSW Department of Industry’s procurement procedures, to select an appropriate expert to develop the HHRA.

What is the proposed risk being assessed by HHRA?

It was proposed that the REP use Pestoff 20R, a cereal-based bait pellet, which contains 20 parts per million (ppm) of the rodenticide brodifacoum, over two applications 14 to 21 days apart, distributed through a combination of bait stations, hand broadcast and aerial application.

A HHRA assessment determined “the likelihood that a given exposure or series of exposures may have damaged or will damage the health of individuals (US EPA, 2016a).” So, in this case, the risk of exposure to brodifacoum from the REP was assessed.

Other Monitoring

An extensive environmental monitoring program has been conducted during and after the REP, including:
  • Soil monitoring after bait distribution. Post operational soil samples have been collected to monitor residues of brodifacoum in the soil. Representative samples have been collected from directly below some toxic bait and at control sites away from bait pellets. Further soil samples will be collected approximately 30 days after bait disintegration and approximately every two months (if required, dependent on results). All tests are conducted at a NATA accredited analytical laboratory.
  • Sampling has been conducted on water bodies on the island (including streams, ocean water, ground water and water tanks) to monitor brodifacoum levels after the bait drop. Water samples were collected within 2 days of each bait drop and four months following the final bait drop. All tests are conducted at a NATA accredited analytical laboratory.
  • Additional samples of milk, eggs and fish were taken as a standard precaution prior to and after baiting.