Backyard hens’ eggs contain 40 times more lead on average than shop eggs

There’s nothing like fresh eggs from your own hens, the more than 400,000 Australians who keep backyard chooks will tell you. Unfortunately, it’s often not just freshness and flavor that set their eggs apart from those in the shops.

Our newly published research found backyard hens’ eggs contain, on average, more than 40 times the lead levels of commercially produced eggs. Almost one in two hens in our Sydney study had significant lead levels in their blood. Similarly, about half the eggs analyzed contained lead at levels that may pose a health concern for consumers.

Even low levels of lead exposure are considered harmful to human health, including among other effects cardiovascular disease and decreased IQ and kidney function. Indeed, the World Health Organization has stated there is no safe level of lead exposure.

So how do you know whether this is a likely problem in the eggs you’re getting from backyard hens? It depends on lead levels in your soil, which vary across our cities. We mapped the areas of high and low risk for hens and their eggs in our biggest cities—Sydney, Melbourne and Brisbane—and present these maps here.

Our research details lead poisoning of backyard chickens and explains what this means for urban gardening and food production. In older homes close to city centers, contaminated soils can greatly increase people’s exposure to lead through eating eggs from backyard hens.

What did the study find?

Most lead gets into the hens as they scratch in the dirt and peck food from the ground.

We assessed trace metal contamination in backyard chickens and their eggs from garden soils across 55 Sydney homes. We also explored other possible sources of contamination such as animal drinking water and chicken feed.

Our data confirmed what we had anticipated from our analysis of more than 25,000 garden samples from Australia gardens collected via the VegeSafe program. Lead is the contaminant of most concern.

The amount of lead in the soil was significantly associated with lead concentrations in chicken blood and eggs. We found potential contamination from drinking water and commercial feed supplies in some samples, but it is not a significant source of exposure.