Backyard chickens can be a source of lead posioning

Last month a local veterinarian had a Berkeley client bring in a very sick chicken.

“It was almost dead,” said Dr. Lee Prutton, of the Abbey Pet Hospital in El Cerrito. Prutton said he put the chicken to sleep and, wondering if it had a contagious disease, sent the body to the state lab for testing. The results: heavy metal poisoning, mainly lead.

The vet is now concerned that people are raising chickens in lead-contaminated urban soils, unaware that the lead can enter the chickens’ eggs that we eat.

Lead poisoning can cause brain damage, miscarriage, high blood pressure and learning and behavior problems, and is especially problematic for growing children, according to the Alameda County Healthy Homes Department.

Last October, the New York Times reported that “…a New York State Health Department study show(ed) that more than half the eggs tested from chickens kept in community gardens in Brooklyn, the Bronx and Queens had detectable levels of lead, unlike store-bought counterparts.”

A study in the 2003 Journal of Veterinary Diagnostic Investigation confirms the transmission of lead from a chicken to its eggs. According to ‘Lead Contamination of Chicken Eggs and Tissues from a Small Farm Flock,’ “The data show a strong positive correlation between (chickens’) blood lead and the concentration of lead in the yolk of eggs… Eggs and chicken tissues containing significant concentrations of lead are a potential human health hazard, especially to young children.”

In Berkeley, backyard chicken keeping is on the rise, but how many chickens are out there is unknown, since licenses are not required. At the Urban Farm Store at BioFuel Oasis on Sacramento and Ashby, a clerk says they sell about 20 bags of chicken feed a day. She estimated at least 500 households in town are raising chickens.

So lead in the soil is something those chicken owners need to know about. It’s also a concern for backyard gardeners, of course.

But Daniel Miller, executive director of Spiral Gardens, the community garden on Sacramento Street, cautioned about being too worried. “It is something we need to be educated and concerned about, but not something to be alarmist about.”

Lead, more than the low, naturally occurring amounts, is all around us in an urban setting, Miller said. The question, he said, is, how much, and how to remediate it.

Ruby Blume, at Oakland’s Institute of Urban Homesteading, agreed. Blume said she gets a lot of questions about lead in soil and has posted an article addressing the issue on the Institute’s website.

Lead can get into soils from lead-paint chips from buildings, past industrial use of the land, and auto fumes. Step one is learning about one’s soil.

Miller said when Spiral Gardens was founded in 2004 they tested the soil, which turned out to be fine. Berkeley’s Ecology Center provides a list of soil testing organizations.

Miller says he likes the University of Massachusetts lab, which is relatively cheap (as little as $9) and provides a comprehensive report, giving the parts per million (ppm) of lead in the soil.

Chickens love to peck in the dirt and dust-bathe. Owners are advised to get their soil tested. Photo: Nancy Rubin

Lead levels of 300 to 600 ppm are typical in East Bay soils, according to Blume. (Naturally occurring levels – of non-toxic lead — are 10 to 50 ppm.) Up to 300 ppm is considered “a safe level” for growing produce, according to the University of Minnesota, but 400 ppm is the “hazard level for bare soil in play areas,” according to federal and state agencies.

That doesn’t mean 400 ppm is necessarily unsafe for growing plants. In such soil, Blume said, almost no lead reaches the fruit of the plant – such as an apple, zucchini or tomato. Very little reaches the leaves or even roots, she said. The biggest danger to the consumer is eating contaminated dirt clinging to the plant, so leafy greens should be washed well. Root vegetables should be washed and peeled.

Soil with higher levels of lead can be remediated with fish bone meal or compost. The phosphates in these materials bind with the lead, turning it into a non-toxic form, Blume said. Planting in raised beds also alleviates the problem.

Blume said she doesn’t think lead need be a huge concern for gardeners, and that she’s more concerned with chickens. Chickens love to peck in the dirt and dust-bathe, she said. She advised people raising chickens to get their soil tested.

Providing a barrier of wood chips or mulch between the chickens and the dirt can lessen the contact with lead. At Spiral Gardens, Miller said, years of composting have built up 2 feet of new dirt under the chicken run.

On Saturday Sept. 7, Miller is giving a free class at Berkeley’s Ecology Center to address gardening and heavy metals. He will cover how to test soil, how to interpret the results and how to remediate. He is also happy to discuss raising chickens, if people would like to, he said. For more information on the class, visit the Ecology Center website. (Register for the free class in advance so the organizers have a head count.)