Certain environmental conditions can cause algae to reproduce rapidly in bodies of fresh and marine water, leading to algal blooms. These blooms, often known as harmful algal blooms or HABs, have the potential to cause harm to human health, aquatic ecosystems, pets, and livestock. Periodically, the Texas Commission on Environmental Quality (TCEQ) is asked to address these HABs in drinking and surface water. While there are no federal maximum contaminant levels (MCLs) for cyanotoxins, the United States Environmental Protection Agency (US EPA) and other agencies have developed screening levels for various types of cyanotoxins. The present work shows the development of acute (short-term) oral toxicity factors and associated health-based screening levels for both drinking water (humans) and for consumption of algal mats/crust by dogs and livestock. A literature search was conducted for peer-reviewed literature and regulatory documents that could be used as a basis for developing acute (short-term) oral toxicity values (i.e., reference doses (RfDs)) for humans, dogs, cattle, and horses. Existing screening levels are presented, as well as candidate reference dose (RfD) values for humans and animals. The RfD values were derived from studies of 30 days or less using standard approaches from US EPA and TCEQ. Short-term screening values were then derived for microcystin-LR, cylindrospermopsin (CYN), anatoxin-a, and dihydroanatoxin-a. These values are helpful when emergency situations arise and TCEQ needs to provide support to other state agencies to protect public health.