Image: UC Cooperative Extension.

Back in 2018 UC Davis began a study of heavy metal contamination of eggs from backyard chicken flocks. The study analyzed eggs from 344 California residences using Coupled Plasma Mass Spectrometry to look for arsenic, cadmium, copper, lead, mercury and and nickel.

The overall results for the study show that the main metal to worry about is lead, though some of the samples showed elevated levels of mercury and cadmium that could be a concern. The maximum lead level found was 27.97 ug/egg which is well over the maximum recommended exposure level of 3 ug for children and 12.5 ug for adults. That said, the average was 1.39 ug of lead.

I was eager to participate in this study since we found elevated lead levels in our soil when we did a series of soil tests back in 2011. Thankfully our egg results came in at 1.02 ug, just under the average level in the study. You’d have to eat a lot of eggs as an adult to go beyond the Federal Drug Administration’s maximum recommended lead intake level, though you could bump up against it if a child ate more than three eggs a day.

I’d suggest that if you live in an older urban location, next to a gas station or other industrial site or a recently burned area you may want to get your eggs tested. Odds are that your backyard eggs are safe to eat but, as the study showed, some of the lead results were well over safe levels.

Here’s what UC Cooperative Extension suggests if you have a lead issue,

Once potentially contaminated areas are identified, it is your job to prevent your chickens from coming in contact with those areas! You may choose to completely remove access to these areas or add clean cover material (soil, mulch, etc.) to reduce contact with or ingestion of contaminated soil. If you choose to use cover material, remember to inspect the cover regularly and add/maintain material as needed.

To further prevent ingestion of contaminated soil, provide chickens’ regular feed in feeders, and avoid scattering feed, including scratch grains and food scraps, on bare ground. Also, avoid feeding chickens unwashed garden scraps from these areas.

Consider providing a calcium supplement, which may help to reduce the amount of lead that gets into chickens’ eggs.

While we got a free test out of the study (thank you UC Davis!), you can have your eggs tested for a fee by contacting the California Animal Health and Food Safety (CAHFS) laboratory (phone: 530-752-8700).