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Studies have shown that eggs from backyard hens contain on average 40 times more lead than store-bought eggs.
Jul
There is nothing better than fresh eggs from your own hens, over 400,000 Australians who raise backyard hens will tell you. Unfortunately, it’s often not just freshness and taste that sets their eggs apart from those from the shops.
Our newly published research* Backyard eggs were found to contain, on average, more than 40 times more lead than commercially produced eggs. Almost one in two hens in our Sydney study had significant levels of lead in their blood. Similarly, about half of the eggs analysed contained levels of lead that could pose a health risk to consumers.
Even low levels of lead exposure are taken into account harmful to human healthincluding, among others, the effects circulatory system disease and lowered IQ and kidney function. Indeed, the World Health Organization has he stated there is no protected level of lead exposure.
So how can you tell if this is a likely problem in the eggs you get from backyard hens? It depends on the levels of lead in the soil, which vary from city to city. We’ve mapped the high- and low-risk areas for hens and their eggs in our largest cities – Sydney, Melbourne and Brisbane – and we’re presenting those maps here.
Our research details lead poisoning in backyard chickens and what this means for urban gardening and food production. In older homes near city centers, contaminated soils can significantly escalate human exposure to lead through the consumption of eggs from backyard chickens.
Snapshot
What did the research show?
Most lead enters the bodies of chickens when they dig in the ground and peck food from the ground.
We assessed trace metal contamination in backyard hens and their eggs from garden soil in 55 Sydney homes. We also investigated other possible sources of contamination, such as animal drinking water and chicken feed.
Our data confirmed our predictions after analysing over 25,000 garden samples from gardens across Australia collected via VegeSafe program. Lead is pollution of greatest concern.
The amount of lead in soil was significantly associated with lead concentrations in blood and eggs of chickens. We found potential contamination from drinking water and commercial feed supplies in some samples, but this is not a significant source of exposure.
In contrast to PeopleThere are no guidelines for blood lead levels in chickens and other birds. Veterinary assessments and research suggests that levels of 20 micrograms per deciliter (µg/dl) or higher can harm their health. Our analysis of 69 backyard hens in the homes of 55 participants found that 45% had blood lead levels above 20µg/dl.
We analyzed eggs from the same birds. There are no food standards for trace metals in eggs in Australia global. However, in 19. Australian Total Diet StudyIn a compact sample of store-bought eggs, lead levels were less than 5 µg/kg.
The average lead level in backyard eggs in our study was 301 µg/kg. This compares with 7.2 µg/kg in the nine commercial free-range eggs we analyzed.
International research indicates that consuming one egg per day with a lead level of less than 100 µg/kg would result in an estimated escalate in blood lead concentration in children of less than 1 µg/dl. This is approximately the level found in Australian children do not live in areas affected by the operation of lead mines or smelters. level of concern used in Australia in the case of testing exposure sources it is 5 µg/dl.
About 51% of the eggs we analysed exceeded the ‘food protected’ threshold of 100 µg/kg. To keep lead in eggs below 100 µg/kg, our modelling of the relationship between lead in soil, chickens and eggs showed that soil lead needs to be below 117 mg/kg. This is significantly lower than the Australian household guideline for soils of 300 mg/kg.
To protect the health of chickens and keep blood lead levels below 20 µg/kg, soil levels must be below 166 mg/kg. Again, this is significantly lower than the guidelines.
How did we map risks in individual cities?
We used our database of metal traces in garden soil (over 7,000 homes and 25,000 samples) to map the locations in Sydney, Brisbane and Melbourne most at risk of high lead levels.
Map: Max M. Gillings, Mark Patrick Taylor, Author provided
Map: Max M. Gillings, Mark Patrick Taylor, Author provided
Map: Max M. Gillings, Mark Patrick Taylor, Author provided
A deeper look at the data revealed that older homes were much more likely to have high levels of lead in the soil, chickens and their eggs. This finding is consistent with other studies that have shown that older homes are most likely to have hereditary contamination due to the past utilize of leaded paint, leaded gasoline and lead pipes.
What can home producers do about it?
These findings will come as a shock to many who have turned to backyard food production, which has increased over the past decade, recently stimulated by the keen escalate in food prices.
People are turning to home-grown produce for other reasons. They want to know where their food comes from, enjoy the safety of food production without added chemicals, and feel a closer connection with nature.
Although urban gardening is an extremely significant activity and should be supported, previous research soil contamination in home gardens in Australia AND uptake of trace metals by plants show that this should be done carefully.
Pollutants have been building up in the soil over the years of our cities’ history. These inherited pollutants can enter our food chain through vegetables, Bee AND chickens.
The risks associated with urban gardening are usually concentrated in vegetables and fruits. Confined attention has been paid to backyard hens. The challenge of sampling and finding participants has meant that many previous studies have been smaller and have not always examined all possible routes of exposure.
Mapping soil contamination risk allows home gardeners and chicken keepers to consider what these findings might mean for them.
Especially in older, inner-city locations, it would be wise to have their soil tested. People can do this in VegeSafe or by a commercial laboratory. Soils identified as problematic can be replaced and hens kept in areas of known neat soil.
The authors would like to thank Tahereh Yazdanparast for serving as first author.
