By LOUISE CARR, Associate Editor and Featured Columnist
Nothing beats a refreshing swim in the ocean, or a quick dip in the pool to work out. Swimming outdoors is a popular pastime in the summer, and during the winter swimming pools offer an ideal way to warm up and keep fit. But did you stop to consider the potential dangers of this seemingly harmless pastime?
We’re not just talking about the obvious potential risk of drowning or getting sun burn when you’re by the ocean. How about the possibility of picking up an infection that causes diarrhea and vomiting? Or even risking harmful changes to your DNA?
Here we take a look at the potential risks of swimming in pools and the open sea, so you can protect yourself and learn how to enjoy this pastime with minimal danger.
What Are the Main Ocean Swimming Health Dangers?
Ocean swimming can be an exhilarating experience, but poor water quality can result in health problems. Water flowing into the ocean may be contaminated by untreated sewage, waste from pets, fertilizer, and other chemicals. It is important to watch out for advisory notices that alert you to poor water quality, and do not swim close to outflow pipes or from a beach that looks obviously polluted.
Does Swimming in Sea Water Raise Your Blood Pressure?
There may be other dangers connected with ocean swimming, too. Many people believe that since the ocean is full of salt, this can cause problems if you suffer from high blood pressure.
Can swimming in salt water make your blood pressure to rise, just as it does when you eat salty food? In reality, it is very difficult to absorb salt through your skin. This would happen with a process of osmosis, and would occur when there is more salt in the water than there is naturally present in the body, and even then there would likely be minimal absorption taking place.
It is more likely that you would absorb more salt by swallowing sea water than through the skin, so it is unlikely that swimming in the ocean will substantially raise your blood pressure.
Is It Safer to Swim in a Pool?
Since the ocean is such a large area and there are many potential hazards that could enter the water and contaminate it, you could logically assume that swimming in a more contained space would be better for your health.
But when a swimming pool is used by people, it needs to be disinfected. And with this comes potential health issues. Chlorination is the most popular method used for treating swimming pool water. Chlorine in swimming pools protects swimmers from a host of dangerous pathogens such as e.coli, salmonella, and rotavirus. But chlorination cannot protect against every waterborne danger.
And too much chlorine can also cause health problems.
When chlorine is added to water it mixes with other agents like urine, perspiration, skin particles, cosmetics, and hair – and this helps form disinfectant byproducts, or DBPs.
And it seems that the human body does not react well to certain DBPs. These substances may cause damage to the lungs, and inflammation in the respiratory system. Other dangers are also linked with the inhalation of chlorine from swimming pools.
We looked at the most common dangers of swimming in chlorinated pools, and also the dangers of swimming in the ocean, based on recent scientific research.
1. Toxic Algae from Swimming in Ocean Water Can Make You Sick
Harmful Algal Blooms are dense amounts of algae that can collect in coastal waters. Sometimes these “blooms” can be toxic to humans or to animals.
Usually algal blooms can be forecast by water experts and in certain cases beaches are closed and people are advised not to harvest shellfish from waters.
A 2016 study from the New York State Department of Health Center for Environmental Health, Albany recorded detail on hospital visits in New York State and found that from 2008 to 2014 there were 228 hospital visits liked with exposure to harmful algal bloom, which occurred at all times of the year. The scientists also reported that the incidence of algal blooms was increasing.
2. Gastroenteritis from Swimming in the Ocean and Pools
The Environmental Protection Agency in the US says that children, the elderly, and people with weakened immune systems are most likely to develop gastroenteritis from contact with polluted ocean water while swimming.
A 2009 study from Monash University, Alfred Hospital, Melbourne, Australia demonstrated that people who reported an incidence of gastroenteritis were more likely to have swum in a pool or river during the last week.
Adults were also more likely to report an incidence of gastroenteritis when they had swam in a pool or in the ocean during the previous two weeks. The researchers concluded that there were “significant associations between all swimming locations and gastrointestinal symptoms” and that “although the incremental risk of recreational swimming is significant, it is relatively small.”
3. Health Dangers of Swimming Near to Storm Drains
A 1999 study from the University of Southern California shows that there are negative health effects associated with swimming in ocean water contaminated by storm drain runoff.
The researchers found that there was an increased risk of a broad range of symptoms including upper respiratory and gastrointestinal illnesses for people swimming closer to storm drains and concluded “there may be an increased risk of adverse health outcomes associated with swimming in ocean water that is contaminated with untreated urban runoff.”
4. Your Blood Absorbs Harmful Chemicals from the Pool
When you swim in a chlorinated pool you have detectable levels of a potentially dangerous chlorine by-product, haloacetic acids (HAAs), in your urine within 30 minutes of swimming, according to a 2011 study from the University of Cordoba in Spain.
The US Environmental Protection Agency puts a limit on HAAs in our drinking water as they are linked with birth defects and with cancer. The researchers looked at 49 people swimming in or working around an indoor and an outdoor pool. They found that these people had levels of HAAs in their urine within around 30 minutes of swimming or exposure to the water. The HAAs were expelled from the body within around three hours.
Children had a higher concentration of HAAs after swimming than adults. Researchers noted that around 90 percent of exposure to HAAs was from swallowing pool water, so it is certainly advisable not to do this while swimming.
5. Swimming in Pools Can Cause DNA Damage
A 2010 study from Universitat Autonoma de Barcelona, Spain, looked at the effect of different kinds of disinfectant mixed with water on mammal cells.
The study showed that “all disinfected recreational pool water samples induced more genomic DNA damage than the source tap water.” This is worrying since DNA damage increases the risk of cancer. In a 2005 study from the California Environmental Protection Agency, disinfectant byproducts caused cancer in rats.
And a 2007 study from the National Exposure Research Laboratory at the US Environmental Protection Agency links exposure to disinfectant byproducts with an increased cancer risk in humans, too. This study looked at 30 years of research into disinfectant byproducts.
6. Does Chlorine in Swimming Pools Increase the Risk of Asthma and Allergies?
There is evidence to say that swimming in pools increases the risk of asthma and allergies, particularly in children, but there is also evidence to suggest this is not the case.
In one 2010 study from the Catholic University of Louvain in Belgium, swimming in chlorinated pools during infancy increased the risk of lower respiratory tract infection.
The study looked at 430 children with an average age of 5.7 years, and found that swimming at indoor or outdoor chlorinated pools before the age of two was associated with an increased risk of bronchiolitis and that child swimmers who developed bronchiolitis showed higher risks of asthma and respiratory allergies later in childhood.
And a 2009 study from the Catholic University of Louvain in Belgium of over 800 Belgian teenagers showed children who swam for longer in pools were more likely to suffer from hay fever, allergies, and asthma.
But a 2011 study from the Centre for Research in Environmental Epidemiology, Barcelona, Spain, which tracked over 5,700 children in the UK over 10 years found no evidence that swimming increased the risk of allergies and asthma.
In fact, the researchers found that “swimming was associated with increased lung function and lower risk of asthma symptoms, especially among children with preexisting respiratory conditions.” It certainly seems that more study is needed to find out which of these two opposing findings is the most accurate.
7. Swimming in a Chlorinated Pool Raises the Risk of Bladder Cancer
The disinfection byproducts produced when chlorine comes into contact with contaminates in swimming pool water are linked with a 1.6-2-fold increased risk for bladder cancer, according to a 2007 study from Universitaet Karlsruhe in Germany. Bladder cancer risk was increased most in people with a certain gene, according to the study, which suggests that there is a certain mechanism at play which results the body dealing with disinfection byproducts in a different way.