UWM Researcher Explores Value of Testing Homegrown Produce for Lead

Sep 13, 2016

Harris Lowell Byers grew up in Georgia loving science and agriculture. Today, he lives in Glendale, remediates brownfields, and is the father of two children. Byers says the scientist and dad in him wanted to find out how much lead might be making its way from the urban soils into vegetables; so he headed back to school to earn a PhD at UW-Milwaukee's geosciences department to try to come up with answers.

“If you have a child who is already at high risk, that’s already living in certain conditions that place that child at high risk for lead exposure, could eating vegetables that have lead in them add to that cumulative exposure?,” Byers asks.

Lead in children’s blood can lead to devastating neurological and developmental problems.

A portion of this year's crop.
Credit Susan Bence

So, to learn more, Byers has been growing vegetables on a UWM rooftop.

He grows in three different types of soils. “This is from the (former) foundry. Those are from residential gardens and the one behind me is from Home Depot. So if you step back you don’t visually get the sense that this beet is being grown in soil that’s got about 5,000 parts per million lead, which is really high, certainly not a soil you would want to have a child exposed to,” Byers says.

READ: One Milwaukee Woman's Quest to Rid Her Soil of Lead

Inside Lapham Hall in the geosciences department, Byers dries the leaves and “fruits” and then grinds them up, reducing each sample to a coin-sized disc.

Credit Susan Bence

Byers places a dozen discs at a time into a dishwasher-sized x-ray machine – called a wavelength dispersive x-ray fluorescence spectrometer.

“Placed right in these cups and it goes into the magic machine and it takes about 15 minutes,” he says.

Voila! In 15 minutes, Byers can read the graph to decipher the lead concentration of each leaf and vegetable he’s grown.

Two years ago, he started analyzing some vegetables right on the rooftop at UWM. He used a handheld x-ray device that measures lead levels in less than two minutes in without needing to dry or grind them up.

“More of a boxy thing with a trigger, sort of Star Trekky, but that device is able to measure lead down to the single digit,” Byers says.

However, it’s expensive. Byers borrowed the equipment for his research, but envisions the device as a way to educate people growing vegetables for their families.

“(They could) bring tomatoes, they could bring their produce and say can you measure lead. I think the possibilities of interactions between parents and those charged with protecting community health become much easier if you have a way to quantify risk or possible exposure,” he says.

Byers can’t let his excitement keep him from the task at hand. He still has a mountain of dried discs to crunch into a dissertation.

But a few things he’s observed so far:

Some of the brightly-colored vegetables he’s raised – such as beets and carrots – contained more lead than the duller varieties.

Byers believes richly colored leaves and vegetables may sequester more lead.

“If I’m right, it could be that one of the best management practices that comes out of this is managing the type of crops that you grow,” Byers says.

And remember the foundry soil he used? Its tomatoes had lower lead levels that the tomatoes grown in city soil.

Byers has a theory on that too.

Fungi in some urban garden soils may make it easier for lead to enter the vegetable. Or as Byers explains, “Mycorrhizal soil Fungi in some urban garden soils may increase the uptake of lead from soil into vegetables.”

He hopes other researchers will pick up his hypotheses and run with them. Byers says he’ll need to get back to his full-time job of remediating brownfields.