What if the key to neurodegenerative disease lies outside the brain?
Environmental exposures don’t cause disease overnight, says Professor Rolf Halden of Arizona State University. They shape risk quietly — often years before we’re aware anything is wrong.
Progress depends on connecting the cumulative work of the research community to reveal:
- Which exposures matter
- When they matter
- How cause emerges across decades of research
That challenge is especially acute in neurodegenerative diseases like Parkinson’s, Alzheimer’s and ALS.
Researchers like Professor Halden, Center Director of ASU’s Biodesign Center for Environmental Health Engineering, show the way. His work intersects multiple disciplines, data science and public policy.
It shows how connecting trusted, peer-reviewed evidence at scale makes change possible.
An unexpected population-level memory
One of the hardest problems in neurodegenerative disease research is time.
Harmful exposures can occur decades before symptoms appear, leaving the original trigger hard to trace.
To tackle this, Professor Halden and his collaborators turned to an unexpected source: wastewater and sewage sludge.
Sludge acts as a population-level memory, capturing cumulative exposure that short-term blood or urine tests miss. Persistent neurotoxic chemicals accumulate slowly — in bodies and in shared waste streams.
Across U.S. states, these signals reveal striking patterns.
What the evidence shows
Across large-scale reviews and meta-analyses, clear patterns have emerged:
Parkinson’s disease is linked to certain industrial solvents, pesticides, and heavy metals, especially in occupational settings.
ALS shows consistent associations with environmental exposures such as formaldehyde and metals including manganese and mercury.
Alzheimer’s, Parkinson’s, and ALS together show higher prevalence in regions where toxic metals like lead and cadmium appear in soil, blood and sewage sludge.
The findings show where risk concentrates — and where prevention may matter most.
How collaboration turns evidence into insight
Progress here is cumulative. Environmental chemists, epidemiologists, neurologists, and data scientists build on one another’s work.
“That’s the point of science. You build on what’s known, and act where there’s enough evidence to do so,” says environmental toxicologist Dr. Susanne Brander, Ph.D, and Associate Editor at Elsevier.
In neurodegenerative disease, evidence is scattered across decades of peer-reviewed research, multiple disciplines, and disconnected datasets.
Progress depends as much on connecting existing knowledge as on generating new findings.
New tools, such as Elsevier’s LeapSpace, help researchers navigate that complexity — exploring trusted literature at scale and tracing insights back to their sources. Their value rests on the quality and transparency of the evidence beneath them.
Used well, these tools can strengthen collaboration, rather than shortcut it.
Connecting evidence at scale only matters if that evidence can be trusted. For researchers working across disciplines, and for policymakers relying on their findings, the question is not just what patterns emerge, but which are robust enough to act on.
“You build on what’s known, and act where there’s enough evidence to do so.”
Dr. Susanne Brander, Ph.D, Associate Editor at Elsevier.
Using trusted research findings to drive societal change
Turning complex science into real-world change depends on trust, especially when research crosses boundaries.
Environmental measurements must be meaningful to neurologists; epidemiology must inform urban planning. Data must be reliable enough to be reused.
This is where the research ecosystem matters.
“If we’re going to make policy decisions based on science,” says Brander, “those studies need to come from reputable, peer-reviewed journals. Policymakers understand that difference.”
Journals make that possible through rigorous peer review, data transparency and shared standards that allow evidence to become actionable insight.
“You can’t do this alone,” Brander adds. “Interdisciplinary work succeeds through collaboration and through open sharing of data and methods.”
“If we’re going to make policy decisions based on science, those studies need to come from reputable, peer-reviewed journals. Policymakers understand that difference.”
Dr. Susanne Brander, Ph.D.
Why environment offers hope
The most powerful implication of this research is the possibility of improving health outcomes. Halden has lived this journey.
In the early 2000s, his team began detecting antibacterial chemicals like triclosan and triclocarban in U.S. waterways —substances largely invisible to regulators at the time. Years of environmental sampling, biomonitoring, and peer-reviewed publication revealed a consistent pattern of widespread exposure, persistence and potential harm.
What followed wasn’t a single breakthrough, but a decade of accumulated evidence, shared through trusted journals, briefed to regulators and debated openly.
“It took a decade,” Halden says. “But we helped drive policy change.”
In 2016, those chemicals were restricted from many consumer products in the U.S., proving that rigorous, collaborative science can reshape the spaces in which we live.
That arc now defines research into neurodegenerative disease. By reducing toxic exposures through cleaner materials, smarter regulation, and better designed environments, researchers see a path to prevention that treatment alone cannot offer.
The most powerful implication of this research is the possibility of improving health outcomes. Halden has lived this journey.
In the early 2000s, his team began detecting antibacterial chemicals like triclosan and triclocarban in U.S. waterways —substances largely invisible to regulators at the time. Years of environmental sampling, biomonitoring and peer-reviewed publication revealed a consistent pattern of widespread exposure, persistence and potential harm.
What followed wasn’t a single breakthrough, but a decade of accumulated evidence, shared through trusted journals, briefed to regulators and debated openly.
“It took a decade,” Halden says. “But we helped drive policy change.”
In 2016, those chemicals were restricted from many consumer products in the U.S., proving that rigorous, collaborative science can reshape the spaces in which we live.
That arc now defines research into neurodegenerative disease. By reducing toxic exposures through cleaner materials, smarter regulation, and better designed environments, researchers see a path to prevention that treatment alone cannot offer.
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