Toxicity: Why the details matter

“Arctic warming is turning Alaska’s rivers red with toxic runoff.”

New York Times, December 16, 2025.

Headlines like the one above illustrate how the word “toxic” is increasingly used without the scientific detail needed to understand what risk, if any, is present. While misuse of the term is common, there are many cases where contamination does pose genuine ecological or human health risks, which is why it is important to use the term carefully and accurately. Journalists, media outlets, environmental groups, and politicians often use the words “toxic” and “toxicity” to attract attention through headlines and sound bites. These terms are powerful, emotive, and often polarizing. Unfortunately, they are frequently used without sufficient technical context. Toxicity is not just a descriptor, but a condition that must be demonstrated with data.

This raises some basic questions. Do reporters and commentators have a working understanding of geology and geochemistry? Is there an effort to review the underlying data before publication? Is there background checking, or an acknowledgement that there are often two sides to a technical story? And how much does political framing influence how scientific information is presented?

The Canadian Council of Ministers of the Environment (CCME) provides guidelines for determining toxicity. These guidelines make it clear that a substance is not toxic by simply existing in the environment but becomes toxic when the concentration and conditions of exposure are high enough to cause harm, emphasizing that toxicity is a matter of degree rather than simple presence. The definition applies most directly to physical toxicity, such as venoms, drugs, gases, and industrial chemicals, where dose, exposure, and pathway determine effect.

The term has also migrated into broader, figurative use to describe harmful social or behavioural conditions, including toxic workplaces and toxic relationships, as well as into popular culture. While these extended meanings may be useful metaphorically, they blur the precision required in scientific and environmental discussions. In geochemistry and environmental assessment, toxicity is determined by exposure, receptor sensitivity, and environmental conditions. Without these qualifiers, the term loses its technical value and becomes a catchall descriptor rather than a measurable condition.

The phrase “toxic chemicals” is therefore often a misnomer. All elements and compounds listed in the periodic table can be harmful at sufficiently high concentrations. Whether a substance is toxic depends not only on its presence, but also on its chemical form and whether it is biologically accessible and biologically available. Media reporting rarely makes these distinctions.

This article focuses on geological and geochemical processes that affect our daily lives, within the theme: What have you done today that did not involve a mineral?

Metal and non-metal leaching are naturally occurring processes that influence surface water, groundwater, soils, and sediments. The environmental impact of these processes depends on the type and concentration of trace elements within the host material, such as the mineral assemblage. Under certain conditions, elevated concentrations of specific elements may adversely affect a receiving environment. Under other conditions, those same elements may pose little or no risk.

A metal is only toxic to its environment if it is present in a form and concentration that is bioavailable at the time of exposure. Bioaccessibility refers to the fraction of an element that can be dissolved and potentially absorbed, while bioavailability refers to the portion that is absorbed and capable of causing biological effects. Bioaccessibility is usually greater than or equal to bioavailability, because not all dissolved material is absorbed by an organism. An element or compound labelled as toxic is not necessarily one that is absorbed by an organism.

The terms minor elements and trace elements are often used interchangeably. Trace elements frequently occur at concentrations near or below analytical detection limits. Their distribution within minerals is established at the time of mineral formation but can change over geologic time owing to variations in temperature, pressure, and alteration by hydrothermal fluids. These processes are site-specific and vary with local geological conditions.

Background concentrations are critical because they establish the local geochemical thresholds against which changes can be evaluated. Many government technical guidelines for concentration limits are generalized rather than site specific. While useful as screening tools, such guidelines can overestimate risk when they rely on total concentration rather than the bioavailable fraction. It is also important to recognize that even when individual substances are below established toxicity thresholds, combined thresholds and cumulative effects may still pose risks. Additionally, advances in analytical methods continue to lower detection limits, which can adjust measured background concentrations and therefore influence the guidelines used to assess potential toxicity.

Trace element prediction is well-established using standard analytical methods, if sampling and analysis are carried out under robust quality assurance and quality control protocols. Sampling quality is as important as analytical accuracy and precision. Inadequate or inconsistent sampling can lead to questionable data, misleading interpretation, and flawed conclusions.

A field example

During Beneteau’s time working at a mine in Ontario in the mid-1990s, the team was required to demonstrate compliance with acute lethality effluent tests using rainbow trout. The test protocol was straightforward. Ten rainbow trout weighing less than 2.5 g were placed in a pail of discharge water, and survival was assessed after 96 hours. If more than five fish died, the water was considered toxic.

What was less straightforward was that different approved testing protocols produced very different results using the same water. Using the test specified by Ontario for site effluent discharge at the time, the results sometimes failed, as more than five fish died during the test period. Under the federal test method (the specific protocol in use at the time is unclear, but it is currently described in Report EPS 1/RM/13), the fish survived, highlighting a clear discrepancy between methods. Beneteau recalls that the federal test required multiple pails of water, whereas the provincial test used only one, and that one of the tests also required aeration.

This presents an obvious question. Was the water itself toxic, or was the test method influencing the outcome? For example, aeration can alter water chemistry by changing oxidation state, metal speciation, and gas exchange. These factors can affect bioavailability and stress aquatic organisms in ways that may not represent actual receiving water conditions.

The lesson here is not that toxicity testing is invalid. Rather, it is that toxicity claims must be interpreted in context. Test design, exposure conditions, and bioavailability matter. Without that context, the word “toxic” can be misleading, even when the result is technically defensible under a specific protocol. All environmental tests should be conducted in replicate over a defined period, rather than relying on a single observation.

As another lesson, Beneteau learned how much effort a mining company will put into protecting the environment. Mine employees care about the environment where they live and work. In the end, neighbouring mining companies collaborated and a pipeline was constructed to the neighbouring mill. This reduced the fresh water supply requirements for the other mine, and the water received additional treatment before discharge.

Geological perspective

On a historical note, Earth has been subject to several periods of intense natural events that could be considered toxic, including anoxic oceans, sulfurous and oxygen depleted atmospheres, volcanic eruptions, tectonic collisions, and meteoric impacts, some of which are associated with the five mass extinctions.

The resilience of Earth, past, present, and future, reflects its ability to adjust to these ever-evolving conditions, transitioning between what may be considered nontoxic and toxic states over time.

Final thoughts

When toxicity claims do not withstand technical scrutiny, the issue does not disappear. Instead, it often shifts from a regulatory discussion into one framed around rights, perceptions, or public pressure. This raises important questions. Would a media article withstand review by professional regulatory bodies? Would it pass scrutiny comparable to that applied under NI 43-101? Has the author consulted qualified professionals, and has the scientific content been reviewed and approved?

In regulated industries such as mining, professionals are licensed, accountable, and bound by codes of ethics. Technical reports require qualified persons. Media reporting rarely meets these standards, yet the terminology used can have real regulatory, financial, and social consequences.

In practice, assessing a toxicity claim requires asking specific questions. What risk is being asserted? Which parameters are involved? What concentration limits apply, and how were they selected? Were alternative methods or site-specific conditions considered? These are technical questions, not rhetorical ones.

The issue therefore becomes not simply whether toxicity is technically justified, but whether conclusions were imposed without adequate justification. When technical language becomes a barrier rather than a tool, readers are left to draw their own interpretations.

Toxicity should be demonstrated, not declared. The words “toxic” and “toxicity” are too often used selectively for headline impact rather than scientific clarity.

The responsibility to address this does not lie solely with reporters. It also rests with geologists, geochemists, mineral processors, and other resource professionals to educate, explain, and respond. 

Bruce Downing is a geoscientist based in Langley, B.C. Donna Beneteau is an associate professor in geological engineering at the University of Saskatchewan. Laura A. Smith is an assistant professor of geological engineering at the University of Saskatchewan.