The report that Israel Air Force pilots who have flown the Lockheed-Martin F-16I advanced combat plane have to be examined for signs of a toxic chemical in their blood to which they were supposedly exposed in the cockpit has raised many questions among toxicologists. The chemical, formaldehyde, is a widely used fixative agent for tissue in medical and scientific labs and an integral component of formica, MDF, bakelite and other substances used for the manufacture of furniture and even car interiors. Prof. Shmuel Yannai, one of the country's leading toxicologists who works in the Technion-Israel Institute of Technology's department of biotechnology and food engineering, told The Jerusalem Post on Monday that it had long been known that formaldehyde use was problematic. "It's used to preserve tissue in histology labs, as it kills every pathogen-bacteria, viruses and others to prevent the tissue from deteriorating without freezing or refrigeration," said Yannai. "This is called the fixation process." Formaldehyde, as anyone who has worked in a histology or school biology lab can attest, is "very smelly. It is problematic, as it harms the respiratory system when inhaled. The tissues in the trachea, bronchi, bronchioles and even the tiny alveoli in the lungs [where oxygen/carbon dioxide exchange is carried out] react to this very volatile chemical and become fixatedâ€š like lab specimens. More recently, it has been found to be a carcinogen, although it is not the most carcinogenic chemical. Nevertheless, there is no safe level of a carcinogen, just as there is no safe level of a mutagenic material that causes mutations in DNA." But formaldehyde, Yannai said, was nevertheless used on a regular basis in labs and in manufacturing because lab workers used protective equipment. Carpenters and factory workers making formica and other products containing formaldehyde know they have to protect themselves, and they are forbidden to put their products on the market either before they have been aired out or after they have undergone polymerization (which takes longer) so the chemical no longer is volatile and does not release any smell. Yannai said he believed that passenger compartments in commercial planes contained formica and other substances made with formaldehyde, and this produced pleasant surfaces on the internal walls of the plane. However, they have been aired out or undergone polymerization so the formaldehyde is no longer volatile. "But there is no reason I can think of why formica is needed inside a cockpit," he said. Formaldehyde is also added to certain colors and used to facilitate drying. It then undergoes polymerization and gives a stronger and more stable color. Sudden and intense heating, however, could cause the vapors to be released, just as small amounts can be felt in a car sizzling in the sun. But there is a partial vacuum in the cockpit of a combat plane which at higher pressure slowed down the escape of vapors from the cockpit, Yannai said. "We have not been told what happened in this specific type of plane, what formaldehyde was doing there and why no other model of plane has had the problem," the Technion toxicologist said. "We need much more information. A cockpit gets hotter and absorbs more solar radiation than a car on the ground. Maybe there is some other explanation that the Israel Air Force knows about. If the combat plane had a problem with its fuel, it could be removed by distillation, but this is something different, and it can't be eliminated this way. Mucous membranes in the nose, mouth, trachea and lungs can be harmed by exposure to formaldehyde. It could affect the mucous membranes of the eyes, but I'm not sure if this is a major problem." In any case, carcinogens can take decades to show up in the form of cancer. "Almost all types of cancer take years to present themselves," Yannai said.