Test for health risk
Clean, safe water is essential for swimming, boating, and enjoying lakes, rivers, and beaches. While most people are familiar with testing for E. coli in recreational water, test results come back typical in 24-48 hours, which does not satisfactorily answer the question: Is it safe to swim now? Not to mention that contributing factors like changes in temperature, precipitation, sewage outflow, agricultural runoff, etc may change the reality of whether it is safe to swim now vs 24-48 hours ago. That is why the gold standard in monitoring swimming locations now suggests a combination of predictive tools and e. Coli testing.
We at Water Rangers have been trialling a new tool called Bactiquick which seeks to answer the question, “Is it safe to swim now?” and give you results in 15 minutes. It does this by testing for endotoxins in the water sample an indicator of potentially harmful bacteria including E. coli, but also a whole host of other gram-negative bacteria such as salmonella, legionella, vibrio and enterocci. These tests are relatively affordable at $65/ test – competitive with lab testing prices, with the advantage they give you a health risk score in 15 minutes!
Together, E. coli testing and endotoxin screening can provide a fuller picture of water quality; one can look to examples where E. Coli alone missed risks caused by other bacteria. Combining the two tools allows for us as community scientists to interpret the results and understand the questions of whether “Is it safe to swim?”. Thanks to field testing tools like R. Card and Bactiquick, it’s now easier than ever to monitor microbial risks.
What are endotoxins?
Endotoxins are toxic components found in the outer membrane of certain bacteria, especially gram-negative bacteria such as E. coli, Pseudomonas, and Salmonella. These toxins are released when the bacteria die or multiply, becoming suspended in the water. This can then be used to calculate the health risk based on the levels of gram-negative bacteria found.
While endotoxins are not living organisms, they can still cause significant health issues-particularly in recreational waters where swimmers, paddlers, and beachgoers may be exposed through skin contact or inhalation of water spray. Symptoms of exposure can range from mild respiratory or skin irritation to more serious flu-like symptoms or even immune system reactions in sensitive individuals.
Bacteria and other risks in recreational waters
Recreational waters can contain bacteria, viruses, and other pathogens that can cause different health problems. Most commonly these lead to skin, ear, or eye infections and stomach illnesses (diarrhea, vomiting). In rare cases, especially for people with weakened immune systems or certain medical conditions, bacteria can lead to severe infections or bloodstream infections. A few of the many organisms and hazards to be aware of:
- E. coli — an indicator of fecal contamination in freshwater; high levels are linked to increased risk of gastrointestinal illness.
- Enterococci — commonly used as an indicator for marine (saltwater) contamination.
- Vibrio spp. (e.g., V. vulnificus, V. parahaemolyticus) — found in warm, salty or brackish water; can cause gastroenteritis and wound infections; some strains can be severe for people with liver disease or weak immunity.
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Legionella bacteria can cause Legionnaires’ disease, a serious respiratory illness often linked to contaminated water systems like cooling towers, plumbing, and construction water sources. Monitoring for Legionella is critical in many industries, including construction, to protect public health
- Pseudomonas aeruginosa — associated with swimmer’s ear, skin rashes, and folliculitis; common in pools, hot tubs, and sometimes natural waters.
- Salmonella, Shigella, Campylobacter — enteric bacteria that can cause diarrheal illness; they have occasionally been linked to contaminated recreational water.
- Norovirus and other viruses — can spread in recreational water and cause acute gastroenteritis.
- Cyanobacterial (blue-green) blooms — produce toxins (not the same as infectious bacteria) that can cause skin irritation, vomiting, and more serious effects.
Because testing for every pathogen is impractical, monitoring programs often test indicators (like E. coli or enterococci). High indicator counts suggest a greater chance of unsafe water for swimming. BactiQuick’s health risk score looks at the combination of ‘gram negative’ bacteria, meaning we can look at health risks from dangers beyond E. coli, which is very exciting for us!
What is E. coli?
Escherichia coli (E. coli) is a type of bacteria commonly found in the intestines of humans and warm-blooded animals. While most strains are harmless and play a role in healthy digestion, some can cause illness, particularly when ingested through contaminated food or water. In recreational water settings, the presence of E. coli is used as an indicator of fecal contamination, signaling that harmful pathogens such as viruses, parasites, or other bacteria may also be present. High levels of E. coli in lakes, rivers, or beaches suggest that the water may be unsafe for swimming or other contact activities, especially for children, the elderly, or immunocompromised individuals.
Why monitor endotoxins and E. coli together?
Historically, E. coli has been the gold-standard indicator for fecal contamination and overall microbial water quality. High levels of E. coli suggest the possible presence of harmful pathogens.
But E. coli alone doesn’t tell the whole story.
Endotoxins, for example, can still be present even when E. coli levels are low—especially if other gram-negative bacteria are active or dying off in the water. In situations like cyanobacterial blooms, sewage overflows, or industrial discharge, endotoxin levels can spike, indicating elevated health risk even when coliform counts seem acceptable.
Monitoring for E. coli allows us to partially interpret the endotoxin results, helping us make informed decisions on whether further investigation to identify other bacteria may be needed.
By using both R. Card (for E. coli) and Bactiquick (for endotoxins), water quality monitors can get a clearer, more responsive understanding of what’s happening at the microbial level.
Rapid testing tools: Bactiquick and R. Card
Bactiquick: endotoxin screening in 15 Minutes
Bactiquick is a rapid field test designed to detect endotoxins from gram-negative bacteria. It delivers a traffic light-style result (low, medium, high risk) within 15 minutes, making it ideal for on-site assessments by volunteers, lifeguards, or environmental scientists.
This test doesn’t detect specific bacteria, but instead measures total endotoxin activity, acting as an early warning system for microbial risk—especially when combined with traditional or molecular testing.
R. Card – home E. coli testing made simple
R. Card is a semi-quantitative colorimetric test specifically for detecting E. coli in water samples. It requires minimal equipment, no lab training, and produces results in 24 hours. All you need is included in our kit and an incubator – which you can get from us as well.
The R. Card shows a colony count depending on the presence and concentration of E. coli, allowing for an easy-to-read indication of potential fecal contamination. It’s particularly useful for monitoring beaches, rivers, and recreational lakes to give you a coarse indication or potential risk from E. coli.
Sample collection and processing tips
Accurate testing starts with proper sampling:
- Use clean, sterile sample cups – we provide instructions on how to sterilize at home.
- Avoid contamination by wearing gloves and using sterile tools
- Collect samples from just below the surface (at least 6 inches or 15 cm down), away from debris or foam
- Process samples within 2 hours of collection, or store them on ice
Both R. Card and Bactiquick come with clear instructions. Following them precisely, especially for timing and temperature, ensures reliable results.
How to interpret the results
Bactiquick (endotoxins):
- Green (<5 EU/mL): Low risk — suitable for recreational use
- Yellow (5–100 EU/mL): Moderate risk — sensitive individuals may be affected
- Red (>100 EU/mL): High risk — swimming may pose health hazards
R. Card (E. coli):
- Water samples are applied to the cards ( in triplicate), then incubated at 35–37°C for 24 hours. After incubation, distinct colonies appear on the card. These colonies are counted manually, and the average number from the three cards is used to calculate the final result in CFU/100 mL.
🇨🇦 Canada (Health Canada)
- Good:
- Geometric mean ≤ 200 CFU/100 mL. The geometric mean is the average of multiple E. coli test results taken over time, used to smooth out daily variations and better reflect the typical bacterial level at a beach or recreational water site.
- No single sample exceeds 400 CFU/100 mL
- Water generally safe for recreational use
- Poor:
- Single samples exceed 400 CFU/100 mL
- Geometric mean above 200 CFU/100 mL
- Water likely unsafe;
🇺🇸 USA (EPA Recreational Water Quality Criteria)
- Good:
- Geometric mean ≤ 126 CFU/100 mL
- No single sample exceeds 235 CFU/100 mL
- Suitable for full-body contact recreation
- Poor:
- Geometric mean > 126 CFU/100 mL
- Frequent exceedance of 235 CFU/100 mL
- Unsafe for swimming; likely to trigger public health advisories
🇬🇧 United Kingdom (UK – Environment Agency)
- Based on EU Bathing Water Directive (2006/7/EC)
- Excellent quality: ≤ 250 CFU/100 mL (95th percentile)
- Good quality: ≤ 500 CFU/100 mL (95th percentile)
- Poor quality: Above these limits
When to use these tests
These field kits are ideal for:
- Public beaches and swimming areas
- Lakes and rivers with frequent algal blooms
- Urban stormwater outflows
- Community science projects and citizen water monitoring
- Events where rapid safety assessments are required
- Areas where access to a lab is restricted or prohibitively expensive.
Why community monitoring matters
As climate change, urbanization, and bacterial blooms increase, tools like Bactiquick and R. Card empower communities to monitor water locally and act quickly. Whether you’re a researcher, lifeguard, park ranger, or volunteer, using these rapid tests can help ensure safer, cleaner recreational water for everyone.
Want to start monitoring your beach?
Get equipped with R. Card and Bactiquick kits from Water Rangers – and be part of the frontline defence against microbial risks in our water. Everything you need is included in the kits, and look out for additional training resources on our website and youtube.
Sharing your results
Don’t forget to upload your data to data.waterrangers.com!
Doing so empowers communities, researchers, and environmental groups to easily collect, share, and visualize water quality data in one accessible place, promoting transparency and informed decision-making. By contributing to this open platform, users help build a comprehensive map, fostering collaboration across regions, and raising public awareness about local water health. All while supporting citizen science and empowering people to protect their waterways. This data is then available for researchers and decision makers!
