So how do you know whether this is a likely problem in the eggs you’re getting from backyard hens?
More than 400,000 Australians who raise backyard chickens will attest to the superiority of fresh eggs from their own hens. Unfortunately, their eggs are frequently distinguished from those sold in stores by factors other than only freshness and flavor.
Our recently released research revealed that backyard chickens’ eggs often had more than 40 times the amount of lead in them compared to professionally produced eggs. In our Sydney investigation, high amounts of lead were found in the blood of nearly one in every two chickens. Similar to that, almost half of the eggs examined revealed levels of lead that might be dangerous to consumers’ health.
Lead exposure is deemed detrimental to human health at even low levels, with adverse effects including cardiovascular disease, lowered IQ, and impaired renal function, among others. There is no safe threshold of lead exposure, according to the World Health Organization.
How can you determine whether this is a potential issue with the eggs your backyard chickens are producing? The amount of lead in your soil, which varies throughout our cities, will determine this. In our three largest cities, Sydney, Melbourne, and Brisbane, we mapped the regions of high and low danger for chickens and their eggs, and we are presenting these maps here.
Our study reveals how backyard hens were poisoned with lead and what this implications for urban farming and food production. People’s exposure to lead from consuming eggs from backyard chickens can significantly rise in older homes adjacent to urban centers due to polluted soils.
What did the research reveal?
As the chickens scrape in the earth and pick food up with their beaks, the majority of lead enters their bodies.
In 55 Sydney houses, we examined the presence of trace metal pollution in backyard hens’ eggs and garden soil. We also looked at additional potential contaminant sources, such poultry feed and animal drinking water.
Our examination of more than 25,000 garden samples from Australian gardens acquired through the VegeSafe program supported our predictions, which were supported by our data. The most dangerous pollutant is lead.
Lead contents in chicken blood and eggs were strongly correlated with soil lead levels. In certain samples, we discovered probable contamination from commercial feed supplies and drinking water, although it is not a substantial source of exposure.
For chickens or other animals, there are no recommended blood lead levels, unlike for people. Levels of 20 micrograms per deciliter (g/dL) or above, according to studies and veterinary evaluations, may be harmful to their health. In the 55 participants’ houses, 69 backyard hens were analyzed, and it was discovered that 45% of them had blood lead levels exceeding 20 g/dL.
The identical birds’ eggs were examined. In Australia or anywhere else in the world, there are no dietary guidelines for trace metals in eggs. Lead levels in a small sample of store-bought eggs, however, were less than 5 g/kg in the 19th Australian Total Diet Study.
In our investigation, the backyard hens’ eggs had an average lead content of 301 g/kg. Comparatively, among the nine commercial free-range eggs that we examined, it was 7.2 g/kg.
According to international studies, children who consume one egg per day with a lead content of less than 100 g/kg are projected to have a lead blood level increase of less than 1 g/dL. That is around the amount observed in Australian youngsters who do not reside in locations where lead mines or smelters are present. Australia uses a 5 g/dL level of concern when looking at exposure sources.
The 100 g/kg “food safety” criterion was surpassed by almost 51% of the eggs we examined. Our modeling of the link between soil lead, chickens, and eggs revealed that soil lead needed to be under 117mg/kg in order to maintain egg lead below 100g/kg. The Australian residential guideline for soils of 300mg/kg is substantially higher than this.
Lead concentrations in the soil must be less than 166mg/kg in order to safeguard chicken health and keep their blood levels below 20 g/kg. Once more, this is far less than the recommended level.
The dangers across cities were mapped in what way?
We mapped the areas in Sydney, Brisbane, and Melbourne most at risk from elevated lead readings using our garden soil trace metal database (more than 7,000 households and 25,000 samples).
A more thorough review of the data revealed that soils, hens, and their eggs from older residences were far more likely to have elevated lead levels. This result is consistent with past research that revealed older homes are particularly vulnerable to contamination from lead-based paint, leaded gasoline, and lead pipes.
What can growers in the backyard do about it?
Many people who have resorted to backyard food production will be shocked by these findings. It has increased over the previous ten years, recently being fueled by rising supermarket prices.
There are other factors as well why people are choosing locally sourced food. They want to feel more connected to nature, experience the security of growing food without the use of pesticides, and know where their food comes from.
Urban gardening is a very important activity that should be promoted, however past research on the pollution of Australian home garden soils and the uptake of trace metals by plants indicates that it should be done with caution.
Over the many years of our cities’ history, contaminants have accumulated in the soil. Vegetables, honey bees, and poultry are three sources of these pollutants that may infiltrate our food chain.
Vegetables and fruits have generally been the main subjects of urban gardening exposure issues. Chickens raised in the backyard have received little attention. Because it was difficult to sample and recruit individuals, many earlier studies were smaller and did not necessarily consider all potential exposure pathways.
Backyard gardeners and chicken owners should assess what the findings may mean for them by mapping the hazards of contamination in soils.
It would be wise to have their soils examined, especially in older inner-city settings. This may be done at VegeSafe or by using a commercial lab. It is possible to replace problematic soils and confine poultry to areas with known-to-be-clean dirt.
EPA Victoria’s Chief Environmental Scientist Mark Patrick Taylor, Honorary Professor at Macquarie University Dorrit E. Jacob, Professor at Australian National University’s Research School of Earth Sciences, and Vladimir Strezov, Professor at Macquarie University’s School of Natural Sciences
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