Residents in Oregon's Coast Range documented herbicide exposure and prompted a government investigation. Three years later, missing sampling data and unexplained pesticide detections left some of the most important questions unanswered.
MKA Risk Advisory | Insights
In April 2011, residents of Oregon's Highway 36 corridor brought state forestry officials laboratory results showing two herbicides in their urine.
The residents lived near Triangle Lake, west of Eugene, in a landscape of private timberlands, rural homes, and small farms. Aerial herbicide spraying following timber harvests had long been a source of concern. Residents reported health problems and suspected that chemicals applied to nearby forestlands were reaching their properties.
They wanted to know whether those applications were responsible for their exposure.
When their concerns remained unresolved, community members arranged their own testing. The results detected 2,4-D and atrazine, herbicides used in forestry and other forms of vegetation management. The findings prompted a multi-agency investigation involving the Oregon Health Authority (OHA), the Environmental Protection Agency (EPA), and other state and federal agencies.
In November 2014, OHA issued its final public health assessment. The investigation had established that residents were exposed to herbicides. But the available evidence did not account for all potential sources, and the planned sampling around subsequent pesticide applications had never occurred.
The central question remained: where were the chemicals coming from?
What the testing established
The first evidence came from residents themselves.
In spring 2011, community members collected urine samples that were analyzed by an Emory University researcher. All samples tested positive for 2,4-D and atrazine. Those findings demonstrated exposure, but not its origin. Both chemicals had potential sources beyond the nearby forestry operations, and the presence of a pesticide or its metabolite in urine does not independently establish which application caused it.
The government investigation sought to examine that relationship more closely.
In August 2011, public health workers collected 66 urine samples from residents of 38 households. Environmental sampling followed in September, including drinking water, soil, and locally produced foods.
The timing was deliberate. Investigators intended to establish baseline conditions during a period when forestry herbicide applications were expected to be relatively limited. A second round of sampling was planned for spring 2012, closer to anticipated pesticide applications. That comparison was important. It could have helped investigators evaluate whether measured exposure changed around spraying events. But the second phase was canceled.
The evidence investigators never collected
In March 2012, OHA suspended its planned follow-up sampling. According to the agency, the locations of anticipated herbicide applications made it difficult to recruit enough nearby residents for a meaningful study. The timing and circumstances of the applications also complicated the sampling design.
These were legitimate methodological concerns. Poorly timed or inadequately designed sampling could have produced results that were difficult to interpret.
The cancellation left a substantial gap.
Investigators could not determine how pesticide concentrations in residents' bodies or surrounding environmental media might have changed during the application periods they had intended to study. OHA acknowledged this limitation in its final assessment, noting that pesticide concentrations in drinking water, soil, and homegrown foods during other seasons and years remained unknown.
The investigation had collected evidence of exposure, but not the full set of measurements needed to evaluate how that exposure varied over time. For residents concerned about aerial spraying, the missing comparison was consequential.
The records revealed another problem
The final assessment also identified a discrepancy involving pesticide application records. After reviewing community-collected urine samples and available application information, OHA concluded that additional sources of 2,4-D and atrazine existed in the investigation area that were not accounted for in the records available to investigators.
That finding did not establish that a timber company had concealed applications or violated reporting requirements. It did establish that the documented applications could not fully explain the detected chemicals. Determining the source of environmental exposure requires more than identifying where a chemical was reportedly used. Investigators must consider application dates, weather conditions, potential transport pathways, chemical persistence, other uses of the same substance, and the timing of biological and environmental sampling.
Records may identify reported activities. Laboratory results may establish the presence of a chemical. Connecting the two requires evidence sufficient to distinguish among competing explanations. In the Highway 36 case, that connection remained incomplete.
What independent investigative research could have added
The Highway 36 investigation required scientific expertise in toxicology, environmental sampling, and exposure assessment. Documentary research could not have replaced that work or established chemical causation on its own.
It could, however, have supported a more detailed examination of the activities and decisions surrounding the investigation. A systematic review of publicly available records could have helped reconstruct the history of pesticide applications, identify companies and contractors associated with documented operations, and compare application dates with residents' complaints and sampling results.
Corporate and property research could have clarified which entities were associated with particular lands and operations during the relevant periods. Regulatory records and correspondence could have helped establish when concerns were reported, how agencies responded, and which decisions affected the evidence ultimately collected.
This work would not have guaranteed a different outcome. Nor could it have overcome the absence of properly timed scientific sampling. But it could have provided attorneys, technical experts, and affected organizations with a more complete account of the documentary evidence, including discrepancies warranting further examination. That distinction is important in environmental disputes, where scientific findings, business operations, regulatory histories, and legal responsibilities frequently intersect.
For litigation counsel, well-organized investigative research can help identify relevant parties, develop chronologies, assess available records, and focus discovery on specific unresolved questions.
For businesses, similar work can inform contractor due diligence, historical compliance reviews, and assessments of environmental or regulatory exposure.
At MKA Risk Advisory, our work is centered on connecting those pieces of information. We bring environmental and natural-resource expertise to corporate research, regulatory analysis, and litigation support, examining the relationships and records that can help clarify complex disputes. The objective is not to reach a predetermined conclusion. It is to establish what the available evidence supports, identify where accounts differ, and determine which questions require further investigation.
The questions that remained
The Highway 36 investigation began because residents wanted to understand the chemicals detected in their bodies and whether nearby forestry operations were responsible. The government's assessment documented exposure and identified limitations in the available application records. It also acknowledged that the intended follow-up sampling had not been completed. Those findings did not prove that any particular company caused the residents' exposure. They also did not establish that forestry applications could be excluded as a source.
For attorneys, businesses, and communities confronting environmental disputes, the distinction matters. A completed investigation is not necessarily a complete account of what occurred. In Oregon's Highway 36 corridor, residents succeeded in bringing their concerns before state and federal investigators. Their evidence helped initiate a substantial public health inquiry. But when the final report was issued, the question that had brought them forward still lacked a definitive answer.
Sources
Oregon Health Authority. (2014). Final Highway 36 Public Health Assessment.
This article examines a publicly documented environmental health investigation. MKA Risk Advisory did not participate in the investigation. The analysis is provided for informational purposes and does not constitute legal or scientific advice.
