Study shows backyard chicken eggs contain 40 times more lead than store-bought eggs

There’s nothing like the fresh eggs from your own chickens more than 400,000 Australians who keep garden chickens will tell you. Unfortunately, their eggs often differ from those on the market not only in terms of freshness and taste.

Our newly published research Found eggs from backyard hens, on average, contain more than 40 times the lead content of commercially produced eggs. Almost every second hen in our Sydney study had significant blood lead levels. Similarly, about half of the eggs analyzed contained lead at levels that could be of health concern to consumers.

Also low levels of lead exposure must be taken into account harmful to human healthincluding among other effects cardiovascular disease and decreased IQ and kidney function. In fact, the World Health Organization specified There is no safe level of lead exposure.

So how do you know if this is a likely problem with the eggs you get from backyard chickens? This depends on the lead content in your soil, which varies across our cities. We have mapped the high and low risk areas for chickens and their eggs in our largest cities – Sydney, Melbourne and Brisbane – and present those maps here.

Our research describes lead poisoning in backyard chickens and explains what this means for urban gardening and food production. In older homes near city centers, contaminated soils can significantly increase people’s exposure to lead from eating backyard chicken eggs.

What did the study reveal?

Chickens get most of their lead when they scratch at the dirt and peck food off the ground.

We examined the contamination of backyard chickens and their garden soil eggs in 55 Sydney households for trace metal contamination. We also investigated other possible sources of contamination such as drinking water from animals and chicken feed.

Our data confirmed what we had expected from our analysis of more than 25,000 garden samples from Australian gardens collected via the VegeSafe program. Lead is the pollutant of paramount importance.

Soil lead levels were significantly related to lead concentrations in chicken blood and eggs. We found potential contamination from drinking water and commercial feed in some samples, but it is not a significant source of exposure.

Unlike peoplethere are no guidelines for blood lead levels for chickens or other birds. Veterinary expertise and research shows that levels of 20 micrograms per deciliter (µg/dL) or more can be harmful to your health. Our analysis of 69 backyard chickens in the homes of the 55 participants showed that 45% had blood lead levels above 20 µg/dL.

We analyzed eggs from the same birds. There are no food standards for trace metals in eggs in Australia or global. However, in 19. Australian Total Nutrition Studylead levels were below 5 µg/kg in a small sample of store-bought eggs.

The average lead content in backyard chicken eggs in our study was 301 µg/kg. This compares to 7.2 µg/kg in the nine free-range commercial eggs we analyzed.

International research points out that eating one egg per day with a lead content of less than 100 µg/kg in children would lead to an estimated increase in blood lead of less than 1 µg/dL. That’s about the level found in Australian children do not live in areas affected by lead mines or shacks. That level of concern used in Australia for examining sources of exposure is 5 µg/dL.

About 51% of the eggs we analyzed exceeded the “food safety” threshold of 100 µg/kg. To keep egg lead below 100 μg/kg, our modeling of the relationship between soil lead, chickens and eggs showed that soil lead must be below 117 mg/kg. This is much lower than the Australian residential soil guideline of 300 mg/kg.

To protect the health of chickens and keep their blood lead below 20 µg/kg, soil concentrations must be below 166 mg/kg. Again, this is much lower than the guideline.

How have we mapped the risks in the cities?

We used our garden soil trace metal database (more than 7,000 households and 25,000 samples) to map the locations in Sydney, Brisbane and Melbourne most at risk from high lead levels.


Lead risk levels for backyard chickens across Sydney. Dark green dots indicate areas with safe lead levels. Light green and yellow dots are areas above the safe lead level. Orange and red dots indicate areas of high concentration. Map: Max M. Gillings, Mark Patrick Taylor, provided by the author

Map of Melbourne showing high and low lead risk areas for backyard chickens
Map of Melbourne showing lead risk for backyard chickens. Dark green dots indicate areas with safe lead levels. Light green and yellow dots are areas above the safe lead level. Orange and red dots indicate areas of high concentration. Map: Max M. Gillings, Mark Patrick Taylor, provided by the author

Map of Brisbane showing high and low lead risk areas for backyard chickens
Map of Brisbane showing lead risk for backyard chickens. Dark green dots indicate areas with safe lead levels. Light green and yellow dots are areas above the safe lead level. Orange and red dots indicate areas of high concentration. Map: Max M. Gillings, Mark Patrick Taylor, provided by the author

A more in-depth analysis of the data showed that older homes were much more likely to have high levels of lead in floors, chickens, and their eggs. This finding is consistent with other studies that have found that older homes are most at risk from legacy pollution from past use of lead-based paint, leaded gasoline and lead plumbing.

What can backyard growers do about it?

These results will come as a shock to many people who have turned to backyard food production. It’s on the rise in the last decade, recently spurred on due to rising food prices.

people are turning to local products also for other reasons. They want to know where their food comes from, enjoy the security of producing food without the addition of chemicals, and feel a closer connection with nature.

While urban gardening is an extremely important activity and should be encouraged, previous studies by Contamination of Australian home garden soils and Trace metal uptake in plants show that it should be used with caution.

In the course of the long history of our cities, pollutants have been deposited in the soil. These contaminated sites can enter our food chain vegetables, honey bees and Chicken.

Exposure risks in urban gardening have typically focused on these vegetables and fruits. Backyard chickens have received limited attention. The challenge of sampling and finding participants meant that many previous studies were smaller and did not always analyze all possible routes of exposure.

By mapping the risks of contamination in soil, backyard gardeners and chicken keepers can consider what the results might mean for them.

In older, inner-city locations in particular, it is advisable to have the floors tested. People can do this VegeSafe or through a commercial laboratory. Soil identified as a problem can be replaced and chickens can be kept in areas with known clean soil.

The conversation

Mark Patrick Taylor, Senior Environmental Scientist, EPA Victoria; honorary professor, Macquarie University; Dorrit E JacobProfessor, Research School of Earth Sciences, Australian National Universityand Vladimir StresovProfessor, Faculty of Science, Macquarie University.

This article is republished by The conversation under a Creative Commons license. read this original article.



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