Borax is a form of boric acid chemically known as sodium tetraborate decahydrate or simply sodium borate decahydrate. It is a common insecticide, herbicide, fungicide and fire retardant. The Safety Source for Pest Management gives it a "least toxic" rating, stating that the key element, boron, occurs naturally in the earth's crust and can often be found in the human bloodstream. Nevertheless, borax is immediately irritant. Long-term contact can result in toxicity. Keep it out of reach of children and use it only where it won't come into contact with people or animals.
According to the Safety Source for Pest Management, the Environmental Protection Agency, or EPA, considers boric acid to be a moderately acutely toxic substance due in part to oral toxicity. The EPA's reregistration document states that a subchronic borax feeding study using dogs resulted in blood and metabolism disorders as well as effects to the testes, endocrine system, brain weight and size ratios among various organs and glands. The Material Safety Data Sheet for sodium tetraborate decahydrate states that human fatalities have been reported from acute poisoning. In lesser doses, borax may simply cause irritation of the digestive tract. If you swallow any amount of borax, seek medical attention. Do not induce vomiting, but rinse your mouth with water and drink 2 to 4 cups milk or water.
Dermal toxicity is another reason the EPA considers boric acid to be moderately acutely toxic. The Material Safety Data Sheet states that the substance may cause skin irritation. For first aid, it recommends flushing skin with plenty of soap and water for at least 15 minutes while removing contaminated clothing and shoes. Then get medical aid if irritation develops or persists. Wash clothing before reuse.
The Material Data Safety Sheet also states that borax may cause eye irritation. Treat eye contamination by flushing eyes with plenty of water for at least 15 minutes, lifting each eyelid occasionally. Get medical aid.
A study published in the December 1985 issue of "British Journal of Industrial Medicine" indicates that borax dust acts as a simple respiratory irritant. Researchers found symptoms of acute respiratory irritation such as dryness of the mouth, nose or throat, dry cough, nose bleeds, sore throat, productive cough, shortness of breath and chest tightness in borax workers who participated in the study. The Material Data Safety Sheet recommends that if you inhale borax dust, immediately leave the exposure area and get out into fresh air. If coughing or other symptoms of respiratory irritation persist, get medical aid.
The Safety Source for Pest Management reports adverse reproductive effects on rats, mice and rabbits. The EPA observed maternal liver and kidney effects, decreased weight gain and decreased fetal body weights. In two studies, at the highest dose levels, the subjects did not produce litters. Prenatal mortality occurred at the highest dose levels in the rabbit study.