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Matt Weir
Principal Consultant

Abstract: This study highlights the importance of repeated sampling to capture trichloramine levels accurately, as concentrations varied significantly within individual pools. Since factors like pool occupancy, ventilation, and time of day affect trichloramine levels, consistent monitoring is essential to ensure a safe environment.

The Air we Breathe

For swimmers and pool workers alike, the characteristic "chlorine smell" at indoor swimming pools is part of the experience. However, it’s not actually chlorine causing that scent—it's trichloramine, a byproduct of chlorine interacting with organic matter like sweat and other nitrogen-based compounds. While it helps disinfect, trichloramine has some serious health implications. In a recent Swedish study, researchers set out to measure airborne concentrations of trichloramine across various types of pools and evaluate its impact on indoor air quality.

Why Trichloramine Matters

When chlorine reacts with organic pollutants in pool water, it produces several disinfection by-products (DBPs), with trichloramine being one of the most volatile. Trichloramine can irritate the eyes and respiratory tract, impacting both casual swimmers and those who spend extended hours in pools, like competitive swimmers and pool workers. Its volatility means it evaporates into the air, where it can be easily inhaled, posing a potential health risk, especially in poorly ventilated spaces.

The Study: Measuring Trichloramine in Swedish Pools

The Swedish study examined trichloramine levels in 72 different pools, divided into four categories: exercise, instruction, adventure, and rehabilitation pools. Over 167 sessions, researchers collected 434 samples to assess trichloramine levels at different times of day, across seasons, and between pool types.

Here’s what they found:

  • Trichloramine Levels by Pool Type: Exercise pools had a geometric mean (GM) trichloramine level of 0.12 mg/m³, while adventure pools averaged 0.20 mg/m³. Rehabilitation pools, used primarily for therapeutic purposes, had the lowest levels, with a GM of only 0.03 mg/m³.
  • Peak Times for Exposure: Levels tended to be higher in exercise and instruction pools during evening sessions, possibly due to higher occupancy or reduced ventilation after hours. Seasonal variations also played a role; in rehabilitation pools, for instance, levels were higher in colder months, likely due to reduced ventilation.
  • Exceeding Public Health Standards: The Public Health Agency of Sweden suggests a trichloramine guideline of 0.2 mg/m³ for indoor pool air. However, about 30% of the exercise pools exceeded this threshold, underscoring the need for monitoring and intervention. Australian results may be similar, but perhaps even more of a concern. Following on from these results in Sweden, an Australian based research project would be worthwhile.

What’s Next?

Understanding trichloramine’s behaviour is crucial for safeguarding public health in indoor pools. Amongst other control measures, advanced air quality strategies - like improved mechanical ventilation design and operational strategies - could significantly help in managing exposure. Additionally, revisiting air quality guidelines could lead to a safer swimming environment.

In summary, while chlorinated pools provide a safe, sanitary environment for swimmers, this study reminds us that vigilance is key to maintaining indoor air quality. For anyone spending time around pools, from casual swimmers to lifeguards, being aware of indoor air quality and implementing proper ventilation measures can make a big difference in promoting a safer, more comfortable experience for everyone.

QED have the experience and know-how to help you determine if you are providing a safe environment for the patrons, contact us for more information.