Potential cyanotoxin exposure while recreating during cyanobacterial harmful algal blooms, and possible exposure mitigation

Abstract

Beale CF, Wei B, Boyer GL, Wigdahl-Perry CR, Yokota K. 2026. Potential cyanotoxin exposure while recreating during cyanobacterial harmful algal blooms, and possible exposure mitigation. Lake Reserv Manag. 42:61–72. Cyanobacterial harmful algal blooms (cHABs) in lakes and reservoirs often contain cyanotoxins such as microcystins (MC), which can lead to various acute and long-term health complications in humans. During cHABs, MC concentrations can exceed local safety thresholds for recreation, forcing management groups to close public swimming areas. Private beaches and public boat launches may remain open, providing a pathway that could expose recreators to cyanobacteria and cyanotoxins. We hypothesized that persons engaged in motorized recreational activities during cHABs could be exposed to measurable quantities of cyanotoxins through repetitive water splashing without full-body immersion, and that weather conditions, innertube pressure, and tow cleat height could affect the MC exposure. A sampling method simulating a person being towed behind a motorboat on an innertube collecting water splashing was developed. Splash collected contained MC ranging from 0.02 to 4.10 µg/L by liquid chromatography with tandem mass spectrometry and was highly correlated to the lake surface MC concentration (R2 = 0.95, P < 0.05). Collected splash volumes correlated to wind speed, wave heights, towing cleat height, and degree of tube deflation. Five minutes of tubing from a low cleat with a deflated tube could expose a person to 7.22 µg MC, while using a higher tow cleat and a properly inflated tube decreased the potential MC exposure to 0.04 µg. Recreators on cHAB-prone waters must be informed about safer recreational practices to reduce potential cyanotoxin exposure.