Moreover, previous research has also pointed out that sand is more heavily contaminated than the water, in the event that the beach is exposed to sewage reflux.

Scientists warn that beach sand could be contaminated with fecal matter and that it poses even more danger that the water does.

If you haven’t already been put on alert by sunscreen ads speaking loudly about melanoma or heard of the possible dangers of jellfyfish and stingrays, a new study at the University of Hawaii will add to the reasons why you should be cautious this summer before venturing out to the beach.

Fecal coliform bacteria is the most common microorganism found in natural waters, which is commonly used as an indicator for organic pollution.

“The different decay rates of wastewater bacteria in beach sand and seawater indicate that beach sand needs to be considered carefully in assessing its impact on water quality monitoring and public health”, the researchers said in the study. The fecal matter originates from humans and a wide variety of animal and bird species, ranging from water animals to the terrestrial fauna of the beaches. Most are part of the normal digestive system, and only some are pathogenic, potentially causing ear infections, typhoid, dysentery, gastroenteritis, hepatitis A, and cholera. While fecal coliform bateria might be found in most waters, there is a degree to which it becomes risky.

The study is published on the journal Environmental Science & Technology.

So while the bacteria levels in the water may force a beach closure until the unsafe levels are flushed away, it takes a much longer amount of time to wipe it out of the sand.

According to the authors, “The differential decay of wastewater bacteria in beach sand and in seawater provides a kinetic explanation to the often-observed higher abundance of fecal indicator bacteria in beach sand”. When this will happen, “No Swimming” traces are usually that you can see at shores.