Unseen Dangers: How Marine Toxins and Venomous Creatures Are Impacting Health
"From toxic algae blooms to exotic snakebites, emerging environmental threats are changing how poison control centers address public health."
Our world is changing at an unprecedented pace. While technological advancements and global interconnectedness bring many benefits, they also create new and unexpected challenges for public health. Among these are the rising threats posed by marine toxins and venomous creatures, influenced by factors like climate change, increased global trade, and the spread of invasive species.
For many years, poison control centers have been the front line of defense against accidental poisonings and exposures to known toxins. However, these centers are now facing a surge of incidents involving previously rare or unknown substances, stretching their resources and requiring them to adapt quickly. From the coasts of France to inland communities, the changing landscape of toxins and venom is demanding a renewed focus on preparedness and response.
This article explores some of the most pressing issues related to marine toxins and venomous creatures, examining how environmental shifts and human activities are contributing to increased risks. It also highlights the crucial role that poison control centers play in identifying, managing, and mitigating these emerging threats to protect public health.
Invisible Threats in Normal-Looking Seafood
Marine toxins are naturally occurring chemicals that can contaminate certain seafood, and contaminated seafood frequently looks, smells, and tastes normal, making contamination difficult for consumers to detect. A set of marine toxins can cause serious poisoning, the most well-known being amnesic shellfish poisoning (ASP) and diarrhetic shellfish poisoning. When humans eat such seafood, disease can result, according to archived CDC general information. However, data on marine toxins are changing rapidly and there are still many unknowns, with marine toxin testing described as a complex challenge.
Regulatory Limits and Three Families of Detection Assays
The EU establishes regulatory limits for marine biotoxins to protect public health, and detection methods include biological, functional, and chemical assays, each with unique advantages. Existing regulations and reference methods are part of the broader analysis of marine biotoxin occurrence, toxicity, and regulatory limits. As naturally occurring, dual-use biological toxins, marine toxins can now be more easily isolated and purified due to novel synthesis methods and equipment, which has raised new control considerations. The U.S. Federal Register has accordingly documented a proposed rule to control certain marine toxins under the Commerce Control List.
Tracing Toxins to Microscopic Origins
Foundational research traced tetrodotoxin through marine food chains, with the origins of the toxin in xanthid crabs presumably coming from red algae of the genus Jania (Yasumoto 2005). It was also reported that the starfish Asteropecten polyacanthus contains tetrodotoxin (Mosher and Fuhrman 1984). Meanwhile, potent ciguatera toxins were traced to Gambierdiscus toxicus, a small dinoflagellate that grows on and around coral reefs and is ingested by herbivorous fish. These milestones established that marine toxins often originate with microscopic organisms and move up the food chain rather than being produced by the fish themselves.
The Rising Tide of Marine Toxins
Marine environments are facing significant disruptions due to climate change and pollution. These disturbances can trigger harmful algal blooms, increasing the concentration of toxins in seafood and creating new airborne threats. Several studies and reports highlight the emergence of new toxicological challenges linked to these changes.
- Ciguatera Poisoning: Cases are now being reported in areas close to Europe, such as Madeira and the Canary Islands, indicating a geographical shift in the distribution of this toxin.
- Palythoa and Zoanthus Corals: These soft corals, popular in marine aquariums, can release toxins that cause severe respiratory and ocular symptoms in aquarium enthusiasts.
- Cyanobacteria Blooms: The increasing frequency of cyanobacteria blooms in fresh and brackish waters produces neurotoxins, nephrotoxins, and dermatotoxins, with potential but not fully understood consequences for both animals and humans.
An Expanding Body of Reviews on Toxins and Detection
A 2020 review on marine biotoxins tracked the research progress and characteristics of marine biotoxin detection technology. A review of human poisoning from marine toxins surveys current data on the symptoms of acute intoxication across several toxin classes, including paralytic toxins, amnesic toxins, ciguatoxins, brevetoxins, tetrodotoxins, diarrheic toxins, azaspiracids, and palytoxins. Springer curates the latest research on marine toxins and cellular mechanisms, highlighting pioneering discoveries and new methods, while ResearchGate hosts thousands of full-text review articles on marine toxins for literature reviews. Together these sources reflect an active and rapidly advancing field.
A Persistent and Underrecognized Hazard
Marine biotoxins are produced by aquatic microorganisms and accumulate in shellfish or finfish through the food web, usually reaching human consumers through ingestion of contaminated seafood, although other exposure routes such as inhalation exist. Recent studies are clarifying the wide distribution of marine toxins in many kinds of organisms and the intoxication mechanism via the food chain, starting from toxin production by microorganisms. Paralytic shellfish poisoning (PSP) toxins and domoic acid are naturally occurring toxins produced by phytoplankton, and marine animals that filter their food from seawater may accumulate these toxins. Despite these well-documented pathways, poisoning from ingesting marine toxins remains an underrecognized hazard, particularly for travelers in the tropics and subtropics.
Contrasting Toxin Classes and Detection Trade-Offs
A comparative analysis of marine toxins examined two hydrophilic and two lipophilic toxins, focusing on their reactivity properties and bioavailability scores, reflecting the diversity among toxin classes produced by marine microorganisms. A comparison of the mouse bioassay with alternative methods shows the bioassay can detect all marine toxins, while alternative methods are more sensitive but cannot detect isolated, unknown toxins. On the food safety side, marine toxins are resistant to standard methods like cooking and are often odorless and tasteless, though fish with scombroid toxins can sometimes have a honey-combed appearance or a metallic taste. These comparisons highlight the trade-offs between broad detection and sensitivity in marine toxin monitoring.
A Call to Vigilance and Preparedness
The challenges posed by marine toxins, venomous creatures, and emerging environmental threats require a proactive and collaborative approach. Poison control centers, healthcare providers, researchers, and policymakers must work together to enhance surveillance, improve diagnostic capabilities, and develop effective treatment strategies. By raising awareness and promoting responsible practices, we can safeguard public health and protect our communities from these unseen dangers.
Expert Bodies Urge Evidence-Based Limits
EFSA's CONTAM Panel has assessed the available data on marine biotoxins in shellfish and identified for okadaic acid (OA)-group toxins a level at which most consumers are protected. Marine toxins are naturally occurring toxic substances, mostly caused by certain marine organisms such as toxic algae but also by bacteria, and they can accumulate in fish and shellfish, causing significant public health concerns. The disaster-risk community describes these biotoxins as capable of causing a wide range of harm. Consumer-oriented sources similarly note that marine toxins include the bacteria and chemicals that contaminate seafood and cause seafood poisoning, underscoring the broad public interest in this hazard.
Surveillance Data and Emerging Toxin Research
A CDC surveillance report documented 402 foodborne disease outbreaks caused by marine toxins reported to FDOSS, resulting in 1,280 illnesses, 96 hospitalizations, and one death, providing a baseline for tracking future trends in marine harmful algal blooms. European research is now examining emergent marine toxins in the North Atlantic and Mediterranean, developing new approaches to assess their occurrence and future scenarios within the framework of global environmental changes. Frontiers has opened a research topic on the occurrence and impact of harmful algal blooms and marine biotoxins, calling for original research, reviews, and perspective articles. These efforts point toward stronger surveillance and forward-looking research as environmental change reshapes toxin distributions.
Why Neurotoxins Pose the Greatest Threat
Most marine toxins vary in toxicity and complexity, and of these, neurotoxins are the most harmful. Neurotoxins disrupt the nervous system by binding to the voltage-gated sodium channel (VGSC), impacting synaptic transmission and having a significant impact on marine wildlife and humans. This mechanism is described consistently across two LGC Standards publications on the complex challenge of marine toxin testing. The systemic difficulty is that the wide variation in toxicity and modes of action means no single testing approach can adequately address the full range of marine toxins.
Fatal Risks and a Shifting Marine Environment
Naturally occurring marine toxins are among the world's most potent poisons, attacking the central nervous system and capable of being lethal in tiny amounts, with marine neurotoxins in particular posing a fatal threat to human health. A case study on fish migration concluded that while different animals are likely to respond in very different ways, two thirds of the species studied would be forced to migrate, some up to 1,000 km, if greenhouse gas emissions continue to rise, moving toxin-bearing fish into new waters. Marine toxin research is complicated by the limited availability of the large quantities of pure toxin needed for toxicological studies. Civilian research efforts, including work in China, have focused on preventing marine toxin poisoning from seafood and shellfish.