According to North Carolina State University and North Carolina-based chemical engineering firm Appealing Products, Inc., recent testing indicated alarming levels of formaldehyde in fish imported from Vietnam and China. Researchers say around 25 percent of fish purchased from supermarkets in the Raleigh, NC area contained potentially dangerous levels of the known carcinogen. The substance was not found in any fish produced in the US.

According to Food Safety News, A. James Attar, Jason Morton and Matthew Schwartz of Appealing Products decided to test a new formaldehyde test developed for a client in Bangladesh by purchasing fish from local supermarkets, intentionally contaminating them and testing them. What they found instead was shocking: one in four fish were already contaminated. The commonality between the contaminated fish was their origin in either China or Vietnam.

Adding formaldehyde intentionally to prevent spoilage can be a problem in less affluent nations, especially those where refrigeration or ice are not always available.

For more on intentional adulteration, check out "Preventing economically motivated adulteration," from the September, 2013 edition of Food Engineering.