Oceans and Human Health: Harmful Algal Blooms and Acute Health Symptoms Among Surfers and Lifeguards
- Author(s): O'Halloran, Christina Lee
- Advisor(s): Colford, John M
- et al.
Oceans and human health is an emerging interdisciplinary field. The oceans modulate our climate and provide food resources, recreational opportunities, and esthetic enjoyment. Marine ecosystems are under threat due to population growth, anthropogenic pollutants, tourist activities, aquaculture production, and global shipping transportation. Additionally, harmful algal blooms (HABs), although naturally occurring, have increased dramatically worldwide. Microbial and chemical contamination of seawater and seafood has had a negative effect on human health. Preservation and restoration of the oceans is critical to the health of marine organisms, marine mammals, and humans.
This dissertation comprises three research chapters. The research question of interest is "what acute health risks, if any, are associated with exposure to seawater?" Chapter one presents a meta-analysis that reviewed acute human health effects associated with harmful algal blooms. Karenia
brevis, a microalgae, produces a suite of natural toxins known as brevetoxins. These brevetoxins were found to be associated with acute health symptoms of nasal congestion, eye irritation, and cough. Specifically, this meta-analysis revealed there was a 3.58 increase in relative risk of eye irritation [95% confidence intervals (CI), 2.00 - 6.42], 2.45 increase in relative risk of nasal congestion (95% CI 1.51 - 3.98), and 2.24 increase in relative risk of cough (95% CI 1.49 - 3.38) associated with exposure of aerosolized brevetoxins.
Chapter two and three examined the acute health effects among lifeguards and surfers. They were ideal participants for these studies due to their high levels of seawater exposure. In both studies upper respiratory symptoms were the most commonly reported acute health symptoms at 21% and 29% respectively. Findings from the surfer health study, in chapter two, demonstrated that surfers
who previously experienced acute health symptoms while surfing during a HAB were 1.63 times more likely to have upper respiratory symptoms than surfers who have not experienced any acute health symptoms during a HAB event (95% CI = 1.09, 2.44). Surfers with housemates with upper respiratory symptoms were 1.72 times more likely to have upper respiratory symptoms as compared to surfers with healthy housemates (95% CI = 1.22, 2.43). Surfers with a physician diagnosis of allergies were 1.41 times more likely to have upper respiratory symptoms in comparison to surfers without allergies (95% CI = 1.01, 1.97).
Chapter three describes the national cross-sectional study of ocean lifeguard. Lifeguards with a history of surfers ear were 2.95 times more likely to have upper respiratory symptoms than lifeguards who did not have a history of surfers ear (95% CI = 1.33, 6.54). Lifeguards who reported they have had acute health symptoms after exposure to a HAB were 1.5 times more likely to upper respiratory symptoms than lifeguards with no such history (95% CI = .72, 3.47).
Gastrointestinal symptoms were 2.49 times more likely among lifeguards with a history of acute health symptoms after HAB exposure than lifeguards who reported no history of acute health symptoms after exposure to HABs (95% CI = 0.76, 8.16). Lifeguards with a history of physician diagnosed anxiety were 1.69 times more likely to have acute stress symptoms after a rescue than lifeguards without a history of anxiety (95% CI = 1.31, 2.17). Lifeguards with a history of physician diagnosed asthma were 1.66 times more likely to experience acute stress symptoms after a rescue as compared to lifeguards without a history of asthma (95% CI = 1.30, 2.11). Additionally, lifeguards with acute health symptoms after exposure to a HAB were 1.42 times more likely to experience acute stress symptoms after a rescue than lifeguards without a history of acute health symptoms after a HAB (95% CI =1.08, 1.86).
In conclusion, evidence from these studies suggests that there is a positive association between HAB exposure and acute health symptoms in humans. Future studies are necessary to assess the human health risks of the different algal toxins produced during a HAB. Additionally, co-occurring bacteria and viruses, with exponential growth, during these HAB events need to be further investigated.