Overlooked Impacts of Circular Economies: Copper Slag Repurposing in Cottonwood, Arizona

Gardenroots: Cottonwood, Heart of the Verde Valley

Copper slag, a hard, solid byproduct of copper smelting, has been widely repurposed as fill material, road gravel, and construction aggregate in Cottonwood, Arizona, and across the Verde Valley. While it may look like ordinary gravel, copper slag can contain elevated levels of heavy metals such as arsenic, lead, and cadmium that may leach into soils and become airborne as dust, posing risks to environmental and human health, particularly for those who live, work, or play near slag-containing soils.

To better understand these exposures in the Cottonwood community, the Gardenroots: Cottonwood, Heart of the Verde Valley project brought community members to the center of the research process. Participants identified questions, co-designed the study, and were trained on sample collection. In total, 13 participants collected 11 soil samples, 12 indoor and 13 outdoor dust samples, and set up 6 PurpleAir air quality monitors. Participants received their results on March 20th and 21st, 2026, at a community-first data report back event. Anyone can explore the deidentified community soil and dust data on the Gardenroots explorer website!

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Results and Next Steps

Community members now have their own data in their hands to contextualize their lived experiences in their environment. However, the sampling for Gardenroots: Cottonwood took place during a period of non-blasting. This means, the company that was repurposing the copper slag did not blast the slag pile for their operations. The blasting occurs when the company explodes part of the slag pile, which is normally an extremely hard, compacted, and solidified mass, to break up the material for processing. During this process, dust is generated from the blast, which community members hypothesize travel off sight and coat community property and homes with black dust. Due to this, blasting was the main environmental and human health concern for community members. Therefore, not sampling during a blasting period did not provide insight into what environmental contamination looks like during active blasting, since no potential dust was being spread across the community. 

The sampling results have left the community with more questions than answers. Many are wondering what sampling during a blasting period would look like. However, the company has started blasting again, which gives us the opportunity to do additional testing after a blast. After speaking with the community, our team decided it would be best to conduct a second round of sampling. I have redistributed dust and air monitoring kits to community members at the end of the report back event. Hopefully, these samples will give the community more insight into whether the blasting impacts the surrounding community. For me as a researcher, although we were unable to collect samples during blasting, I think the initial data will serve as a great comparison point for the next round of samples. Having this comparison point will strengthen our understanding of these processes and help with dissemination of impacts!

Lessons Learned

Research is a cycle, not a process. When one question is answered, another one appears. This cycle repeats, sometimes branching off into new variations and projects. Sharing and co-designing this process with the community members of Cottonwood has taught me how to integrate community concerns and questions into research. Each person involved in the study has their own insights and questions they want to investigate. For example, the community were the ones to push for this second round of testing and gave insight for how long to wait after the blasting to sample. Weaving these ideas together, we were able to create a plan that brought together the perspectives of the community. Despite the lack of data during a blasting from the first sampling period, community members were very thankful for the chance to have additional testing completed. 

Overall, during the last year of this project I’ve met countless community members who only want the best for their neighbors and children. I am so thankful for the experiences I have been given as part of this project, and I am excited to continue working with the community in the future. I hope, more than anything, that the results of this collaboration give voices to the community members who feel as if their concerns have been ignored for far too long.