New research points to dangerous “lead poisoning” among backyard chickens, but should we be concerned?

Written by Dr Paul Harvey on 16 Aug 2022 - 11:39am.

New research published in August by researchers at Sydney’s Macquarie University has caused concern among home gardeners and chicken keepers about possible “lead poisoning” of chickens and their eggs. But chicken keepers should be alert and not alarmed.

A recent study has ruffled some feathers after revealing that backyard chickens and their eggs may be “poisoned” by lead. The study published in Environmental Pollution by researchers from Macquarie University has posed the question: should householders be alarmed, or just alert? Lead researcher and PhD candidate Sara Yazdanparast said “our findings support the need for close monitoring of potential toxic metal concentration in local produce,”

Sixty-nine chickens and their eggs from fifty-five backyards across Greater Sydney were examined in the study. Each chicken had a blood sample and an egg collected. These were then analysed by the researchers for their concentration of lead.

Lead is a heavy metal that has impacts on brain development, among other negative health outcomes. Many home gardens, particularly those in older parts of cities have detectable concentrations of lead in their soils due to the historic use of lead in paint and fuel. The study “demonstrates that contaminated urban garden soil poses the greatest potential risk to backyard chickens in terms of lead exposure,”

“Chickens receive metals during their lifetime through the food chain or via close contact with the environmental contaminants through several factors, such as absorption (e.g. soil and occupational chemicals), ingestion (e.g. drinking water and food) and inhalation from air into livestock, and are able to accumulate pollutants in their eggs and tissue during the breeding period,” Sara said.

Chickens can be exposed to lead through soil, food and water. Image: Giallopudding, Piaaby.  

For the first time in Australia, Sara modelled soil lead concentrations and determined how much lead can be in the soil before chickens begin to show signs of poisoning.

“The study modelling demonstrates that soil lead concentration threshold of 96 micro grams per kilogram may be associated with the maximum egg lead concentration guideline value, and the recommended blood lead levels with sub-clinical signs for chickens,” Sara said.

The research has very important implications for environmental regulators and Sara has called for more action.

“To prevent health risks, local governments and the Environment Protection Agency should adopt more stringent measures to reduce emissions of heavy metals and monitor heavy metal contamination in the environment and domestic products. Health risk assessments should be conducted with relevant background exposures and establish health-based standards instead of the presence of hazardous substances alone,” Sara said.

According to Sara, eggs purchased from the supermarkets contain much lower concentrations of lead than those grown at home, “the concentrations measured in Sydney backyard chicken eggs compared with commercial farm free-range eggs showed that residential backyard chickens had significantly higher concentrations of Pb than commercial farms,”

For homeowners that are concerned about lead impacting their backyard chickens, Sara said that people can take a few simple steps to reduce the risk of exposure.

“If there is any concern over soil lead and backyard products, submitting appropriate environmental samples (such as soil, water, feed, wood chips) for analysis will help to find the sources,” Sara said.

Sara also advised “if any chicken presents illness, it should undergo heavy metal screening and any precautions must be considered to identify and reduce the source of contamination in the environment. This may include elevating coops, reducing contact of chickens with the soil, and avoid using eggshells in compost do the risk of re-contamination,”

Sara emphasised that the aim of the research is not to deter home owners from keeping chickens, but instead wants the work to “make recommendation for risk assessment and for soil screening and clean up values in order to ensure chicken safety and mitigate human exposures through consumption of home-grown chicken products.”