Endotoxins
What is endotoxin?
Endotoxins are tiny pieces found in the outer layer of some bacteria, especially ones like E. coli, Salmonella, and Pseudomonas. When these bacteria die or break apart, they release endotoxins into the water. Even though endotoxins aren’t alive, they can still make people sick. While endotoxins are not bacteria themselves, they can cause significant health issues in humans, especially when present in water used for recreation, drinking, or medical purposes. They also can be used to indicate the possible presence of bacteria that can make us sick!
Exposure to endotoxins, and the bacteria that produce them, in recreational waters has been linked to respiratory issues, skin irritation, and flu-like symptoms. In more serious cases they can trigger strong immune responses and septic shock.
Why are endotoxins important in recreational water monitoring?
Endotoxins are increasingly recognized as important indicators of microbial water quality; especially in warm, nutrient-rich environments where bacterial blooms (such as cyanobacteria) can occur. Because they are released from bacterial cell walls, endotoxins provide a signal that bacterial degradation or cell death has occurred, which may indicate water that is unsafe for contact.
Monitoring endotoxin levels in recreational waters helps to assess potential risks to public health, especially for sensitive groups like children, immunocompromised individuals, and people with respiratory conditions. Unlike traditional bacterial tests that look for live organisms, endotoxin testing reveals a broader picture of microbial activity and potential toxicity even when the bacteria themselves are no longer alive. Testing for endotoxins may indicate health risks even in situations where tests for bacteria like E. Coli would indicate conditions are safe for swimming.
How can we measure health risks at the beach using endotoxins?
Endotoxins are measured in water samples using units called Endotoxin Units per millilitre (EU/mL). Traditional testing methods are highly sensitive but require laboratory environments, skilled technicians, and can be expensive.
However, more accessible field-based methods are emerging, such as Bactiquick. These rapid tests allow volunteers and researchers to test for endotoxins on-site with minimal equipment. While not as precise as lab-based methods, they are fast, affordable, and effective at detecting elevated endotoxin levels, making them ideal for early warning or screening purposes.
Recommended guidelines for endotoxins in recreational water
There are currently no universally adopted recreational water guidelines for endotoxins, but several health authorities and research bodies provide reference values. For example:
- < 5 EU/mL — Generally considered low risk for recreational exposure
- 5–100 EU/mL — Moderate risk; may cause mild symptoms in sensitive individuals
- > 100 EU/mL — High risk; may pose significant health hazards, including respiratory or systemic effects
Testing endotoxins with bactiquick
In 2025, Bactiquick became available to help access to endotoxin monitoring.
- Bactiquick is designed for ultra-fast field testing, give you a traffic-light style result (green, yellow, or red) in just 15 minutes, showing if there’s a low, medium, or high risk in the water. It’s useful for quickly screening a recreational water site to understand health risk. Traditional methods that rely on coliform testing typically take 24-48 hours.
These kits can be used by staff, researchers, and community volunteers to monitor water quality in lakes, rivers, beaches, or areas affected by algal blooms or sewage overflows. Testing in conjunction with traditional coliform testing methods can confirm whether higher endotoxin results may stem from other bacteria that may escape detecting in traditional testing protocols. Test results with high endotoxin risk, but low in e. coli may indicate the presence of other bacteria that can be problematic for human health such as Salmonella or Legionella
Sample collection and processing protocol
While Bactiquick is easy to use, proper sample collection is key for reliable results:
- Collect water in clean, sterile containers
- Avoid cross-contamination by wearing gloves and using clean tools
- Test the sample within 2 hours of collection (or store on ice if delayed)
- Follow the instructions specific to each test kit for timing, temperature, and reading results
Samples that test positive (above threshold) using these kits may require confirmation through laboratory-based testing or more advanced endotoxin quantification methods.
Predicting endotoxin risk at the beach
Just like with E. coli, models are being developed to forecast endotoxin levels using historical data, water temperature, weather, and the presence of bacterial blooms. These predictive tools can help beach managers and public health officials issue warnings before conditions become hazardous.
Why should you monitor for endotoxins?
Endotoxins are an emerging concern in water quality monitoring, especially in areas prone to algal blooms, high bacterial activity, or poor sanitation infrastructure. With tools like Bactiquick you can be part of the solution-helping to identify and mitigate microbial risks before they affect public health.