Visitors to the Barton Creek Greenbelt can once again play in the water. Levels of a toxin called cylindrospermopsin have fallen well below EPA guidance values for recreational use. Cylindrospermopsin is one of several cyanotoxins which can be produced by cyanobacteria, also called blue-green algae. The City of Austin originally issued a warning about swimming at Sculpture Falls after water samples taken on September 9 contained concerning levels of cylindrospermopsin. Two recent water samples have shown much lower levels of the toxin.
The highest reading of cylindrospermopsin was 81 micrograms per liter (µg/L) in late September. However, two consecutive readings in October were 0.1 and 0.01 µg/L. For recreational use, the EPA guidance value is 15 µg/L.
It is possible that the higher toxin levels or a different cyanotoxin will return without warning in the future. This is more likely when the flow drops. People should use caution and avoid swimming if the water is warm, if it appears stagnant, if there’s scum or film on the water or if there are mats of algae. This is true for other natural water bodies as well. You should also avoid swimming for a few days after heavy rainfall when bacteria levels tend to be higher. There can be physical dangers in natural water bodies with uneven depths, debris, slippery surfaces and strong currents.
People who are exposed to cyanotoxins including cylindrospermospsin by swallowing contaminated water may experience the following symptoms: stomach pain, headache, neurological symptoms like muscle weakness or dizziness, vomiting, diarrhea, or liver damage. People exposed to cyanotoxins through touching or swimming in contaminated water or breathing in droplets may experience skin, eye, nose, throat, and lung irritation. Seek medical treatment immediately if you believe you have been exposed or call the Texas Poison Control Center at 1-800-222-1222.
Although there does not appear to be any immediate risk to dogs, dog owners may want to keep their pets away from the water. The harmful algae could quickly return without warning, and dogs are more susceptible to some toxins, and several have died when exposed. Symptoms in dogs may include excessive salivation, vomiting, fatigue, staggered walking, difficulty breathing, convulsions, and liver failure. Seek veterinary care immediately if your pets seem sick after going in or near water.
There is more information about harmful algae at AustinTexas.gov/Algae. Please call 3-1-1 to report possible illness in people or pets from harmful algae.