To date, there has been little research done on the effects of radon in drinking water causing health issues in horses. A few studies have looked at the effects of radon-contaminated water on human health. Most health-related issues with radon are a result of inhalation of the gas. It is not known to what extent radon is absorbed through the stomach lining in humans. If you are concerned that you have high levels of radon in the ground water supply that your horses drink, you should have the water tested. If levels are high, you can use water-mitigation techniques to release the gas from the water. One such method is diffused-bubble aeration which injects air (usually as bubbles) into water. The radon moves from the water to the bubbles as they rise through the liquid. The radon-contaminated air leaves the water when the bubbles reach the surface and is vented out. If you believe you have an issue, you should contact the local office of the Environmental Protection Agency for assistance and proper mitigation of the radon in your water.