TBHQ is the acronym used to describe tertiary butylhydroquinone, which is an antioxidant that comes from petroleum and is related to butane. It is often used as a preservative, applied directly onto food, such as high-fat prepackaged and processed food items and fast food. Like many chemicals, if taken in great excess, it can be toxic. Although more research needs to be done, side effects have not thus far been clinically demonstrated in the quantities that people usually eat.
TBHQ reduces what is referred to as oxidative deterioration in foods it is applied to -- in other words, it acts as preservative by delaying the onset of rancidness. It also therefore extends shelf life of processed foods.
As a food additive, the FDA allows TBHQ to make up no more than 0.02 percent of the total oils in a food, according to a report in the 2004 "European Food Safety Authority Journal." Consuming up to a gram of TBHQ can cause variable toxicity, and up to 5 grams can be fatal. For perspective, it would take 312.5 fast food chicken nuggets, if they contain a full 0.02 percent of TBHQ, to consume a single gram.
Consuming high doses of TBHQ -- between 1 and 4 grams, approximately -- can lead to a variety of negative symptoms, including nausea, vomiting, ringing in the ears, delirium and collapse. But the sheer amount of food consumption necessary to be afflicted by TBHQ toxicity generally makes these symptoms extremely rare.
Cancer Causing Potential
In toxicity studies, long-term, high-dose TBHQ administration in lab animals was linked to the development of cancerous precursors in the stomach, as well as DNA damage. But unlike other antioxidant additives, it did not cause lung lesions in laboratory animals. However, TBHQ can make cancer cells resistant to chemotherapy agents, according to a study in the June 2008 issue of "Carcinogenesis," and a study in the June 2014 issue of "Food Chemistry" notes that TBHQ can fragment DNA and cause damage to human lung and umbilical cells.
TBHQ in Children
There has been some anecdotal evidence that TBHQ can cause anxiety, restlessness, and aggravation of attention deficit hyperactivity disorder, or ADHD, symptoms, although there have been no clinical studies that show any link between food additives and behavioral disorders in children.