Heavy metal levels from MRI slag have minimal health affects
Arizona Department of Health Services officials announced on Thursday, March 19, that risks related to the Cottonwood slag pile were limited to untreated private well water, frequent soil contact in areas with high arsenic concentrations and near the Veteran of Foreign Wars Post on windy days for those with air sensitivities, like asthma.
The concern comes from the Minerals Research Inc. slag mining operation at Birch and Cherry streets, including a large slag pile on the property.
Several heavy metals, the main concern of which was arsenic, are natural in the region and the Verde Valley. These include cadmium, manganese, copper, lead and aluminum.
The concern from the heavy metals other than arsenic were minimal, Arizona Department of Environmental Quality Senior Hydrogeologist Hazel Cox, Ph.D., said.
The presentation at the ADEQ community meeting in the Cottonwood Recreation Center, included nearly two hours of reviewing soil testing results and methodology.
ADHS’ recommendations are based on the amount and duration of exposure, Environmental Epidemiology Office Chief Hsini Lin said, which can fluctuate greatly depending on individual risk factors like age, genetics and lifestyle.
She said no health concerns were identified via air health evaluations for the Cottonwood Kids Park, and there were no heavy metal concerns for the VFW post.
The VFW location did have some concerns on high wind days; the particulate matter up to 10 micrometers could affect sensitive populations including those with asthma.
“Our main recommendations include limiting your outdoor activity when it’s windy,” ADHS Toxicology & Surveillance Program Manager Mya Davis said. “So this might include checking the weather forecast, planning your day around when it’s extra windy, and keeping your home closed during those days.”
The majority of data comes from studies done in 2024 and 2025, ADEQ Air Quality Division Director Daniel Czecholinski said.
The MRI facility was inspected on Feb. 17, a day there were no operations, and the slag pile was blasted on March 9, which helped discern the effect it has on the air quality in the area.
He said no violations were found for either inspection.
The opacity caused by the blasting was about 9.17%, below the federal limit was 40%.
Soil
The main pathway arsenic could be an issue is through the soil.
“We have some recommendations for areas one and two, which was in the VFW area,” Cox said. “There needs to be some actions to potentially remove some soil, or perhaps some areas to prevent exposure to the soil that’s in that area.”
She said there also needs to be some added stormwater pathways protection to prevent spreading. It isn’t above U.S. Environmental Protection Agency standards, but it is possibly a concern for the future.
For area three, or the former smelter stack property which goes across State Route 89A near River Bible Church, Cox said right-of-way user exposure could be a concern and recommended fencing it off, although the use of it is pretty small already, she said.
“A lot of [sample areas in areas four and nine, the Verde Valley Medical Center right of way and parking on the former smelter property] already have a gravel cover, which is great, because when we took our samples, we scraped the gravel back to get to the soil. And so we just want to make sure those areas, it’s maintained, and so people aren’t actually exposed to the soil.”
Areas five through seven, which include the former slag pile location and a nearby slope, found no exposure.
The residential area eight recommendations included minimizing dust exposure and possible soil replacement in hot spot areas, which are available on azdeq.gov.
There were several areas of concern, which means only that one example was higher than the background arsenic levels, not necessarily by how much.
Area 10 of the search, which includes the Kids Park, was one area of concern.
“We did have one sample collected in 2024 that came in at 29.6 milligrams per kilogram, which is over 29.5 milligrams per kilogram [the background level] by 0.1,” Cox said.
She said it was the highest arsenic concentration sample taken from the park, and no exposure concerns as long as the turf is replaced as needed.
Other Recommendations
ADHS officials said there are other precautions locals can take to limit their exposure to arsenic
“One I do want to point out … is avoiding eating in dusty areas,” Davis said. “We know that it’s beautiful here. The weather is lovely most of the year, and a lot of you likely like to eat outside or in parks. So if you do like to do that, we recommend taking a tablecloth with you so that you can limit any extra dust that you might be accidentally eating or wiping the surfaces down before you’re sitting down to eat.”
The public water supply in Cottonwood had levels of arsenic below the EPA standard, Lin said, but private well owners should get theirs tested, because two private wells tested had “arsenic levels that could affect health with long-term drinking use if untreated.”
“Those of you who do have children, as Hsini mentioned, it’s very normal for them to explore their environment,” Davis said, “but if you do notice that they are starting to eat a lot more soil than usual, up to a teaspoon-size amounts, please talk to their pediatrician about that behavior.”
