By Udaiyaa Bommudurai
t’s a hot summer morning, and you are roasting in the heat, so you decide to go to the beach. The water is cool and feels amazing against your burning skin. You spend the day swimming and taking a break from the scorching sun. This is the vision many people have in summer, especially those close to beaches. How would it feel if that vision was deemed unsafe, especially for children, because of feces in the water?
When people are exposed to fecally contaminated waters, they are at increased risk for gastrointestinal, respiratory, and skin infections. Children are known to stay in the water for longer periods of time, ingest more water while swimming, and have generally weaker immune systems than adults. Certain bacteria, such as Shiga-toxin producing E. coli, can cause mild symptoms in adults, but be life-threatening in children. Previous studies have concluded that there is a higher association between gastrointestinal illnesses and Enterococcus exposures among children 10 years of age and under, across the various conditions studied. Enterococcus are a genus of bacteria that exist in the gastrointestinal tract, and are often found in feces. They also serve as indicators of other pathogens in the water. Researchers associated with the EPA, UCSF, UC Berkeley, and Southern California Coastal Water Research Project analyzed the risks associated with increased amounts of Enterococcus spp. for different age groups across different health endpoints, exposures, and sites. Health endpoints are the outcomes the researchers expected would occur when subjects were exposed to the contaminated waters.
Recreational waters are usually monitored and tested for the fecal indicator bacteria Enterococcus and E. coli. Usually, Enterococcus and E. coli aren’t harmful on their own, but when they’re found in high concentrations, they can indicate the presence of more serious pathogens, usually those associated with sewage and other fecal contamination. Lots of research has been done previously, regarding the links between levels of Enterococcus, E. coli, and other fecal indicators in recreational waters, and the risk of illness among those who swim in the water. What sets this study apart from previous studies about waterborne infectious diseases is how it also screened for other illnesses, such as respiratory, in addition to on top of gastrointestinal. This allowed researchers to create a more comprehensive analysis of risks between children and other age groups.
Gastrointestinal illness was considered anything with gastrointestinal symptoms that had lasted more than three days or led to a physician visit. Respiratory illness was anything that had at least two of the following symptoms: cold, cough, sore throat, runny nose, and fever. Everyone surveyed was simply an individual at the beach that was offered the opportunity to participate. The participants were split into three main groups: children (12 and under), older children (over 12), and adults (18 and over). Different children’s age groups were categorized as 4-12, 4-10, 6-10, and 6-12. The groups were intentionally overlapping because this allowed researchers to compare alternate categorizations for children with the rest of the population.
The beaches in this study came from all over the US, ranging from Indiana to Ohio, to California. Most of them were considered human-impacted because of discharges from nearby wastewater treatment plants. This means the people swimming there were expected to be more at risk because human sources of fecal contamination contain higher levels of disease causing microbes. Samples of water were collected at different times and locations every day at every site. The Enterococcus numbers were transformed by log10 and averaged to estimate the water quality on any given day.
All together, there were about 83,452 participants, and children 12 and under made up about 20-25% of the population. At least 70% had some contact with water and 27% actually stayed in the water for longer than an hour. The participants were interviewed over the phone approximately 10-14 days after the beach visit and asked to describe any illness they might have experienced. Results from this study confirm previous associations between exposure to Enterococcus and gastrointestinal illness. However, this goes above and beyond by providing evidence that the association is affected by the intensity of exposure, site characteristics, and age.
There were four main insights regarding the risks of swimming in fecally contaminated water. The first was that gastrointestinal symptoms were associated with all age groups, but respiratory symptoms were only also present in children. The second was that children were at a higher risk of illness after swimming than other age groups. The third insight was that associations between fecal contamination levels and swimming-associated illness depended on the sources of fecal contamination. There were stronger associations when the feces came from human sources. The fourth insight was that for more intense exposures, such as swimming for longer than an hour, or consuming water while swimming, there was an increased risk of illness. These insights are important for beach-goers to learn about.
In the United States, and other countries, many people enjoy going to natural parks, lakes, beaches, and many other recreational water areas. Living in California, people go to the beach extremely often, and it’s important to know what they’re exposing themselves to. Not only that, but parents would be very interested in learning about something that has the potential to severely harm their children. The parks themselves could warn people about the potential threats and educate beach-goers. The results of this study highlight how the source of fecal contamination and the intensity of swimming exposure are important factors to consider when looking at the association between Enterococcus and illness. The greater the population of Enterococcus, the more likely there are other pathogens in the water that can cause sickness. This information could be useful for the EPA, CDC, or other government organizations involved in public health. Knowing why swimmers are getting sick could help them come up with policies, such as improving wastewater treatment or moving sewage plants away from recreational centers.