NOTE FROM THE AUTHOR: This "Question and Answer" was written and sent to the Forum with the sole purpose of answering a toxicological question that could be of interest to many. It is neither the author's intention to educate or instruct members of the Forum nor to flood the members' Email with unnecessary information. With that in mind, attached is his reply to a question raised by a member of the Forum.

QUESTION : Ong Quang oi! Neu co the duoc xin Ong viet cho mot bai ve viec su dung nhung cup va hop bang foam de dung thuc an, co nguy hai gi cho suc khoe khong,vi toi moi co mot nguoi khach hang cho biet rang co ta di mua ca kho Food To Go, mang ve nha de vao microoven ham nong, cup foam bi chay dinh vao do an, nhung co ay van mang ra an, vai ngay sau thay dau bung, di Bac si cho uong Donnatal khong het dau, goi dien thoai den nha thuoc hoi y kien xem co gi nguy hiem den tinh mang khong,toi ben nghi toi Ong, xin cho biet y kien , Cam on nhieu, Tran Duc Hieu.

WHAT'S INSIDE THAT CONTAINER? Foamed cups, trays, egg cartons, etc. are made of polystyrene foam products, which are 95 percent air and 5 percent polystyrene. The foam is also referred to as styrofoam, which is a trade name of polystyrene made by Dow Chemical. Polystyrene is made from styrene, a petroleum by product, through the process of polymerization. The polymerization reaction has, in a way, inactivated the biological activities of styrene (a monomer). Styrene, commercially available since the 1930s, was first used in the manufacture of synthetic rubber and, later on, as automobile parts, electronic components, boats, etc. Styrene is also present in many foods and beverages, including beef, strawberries, peanuts, and coffee beans. It is also approved by the US FDA as a flavoring agent. While styrene may have some toxic properties, polymerization has made polysterene non-toxic since polymers, in general, cannot be absorbed due to its huge molecular weight. Nevertheless, it should be remember that all packagings (including polystyrene, paper, plastics, etc.) contains substances that can migrate or transfer to food or beverage. Leaching of a small amount of styrene would not be unusual, especially when the container melts. At high doses (emphasis added), styrene fume is irritating to the eyes, skin, and mucous membranes. Signs and symptoms of exposure may include fatigue, headache, CNS depressant, muscle weakness, dizziness, and significant irritation of the esophagus and stomach. The International Agency for Research on Cancer (IARC) has determined that there is inadequate evidence for carcinogenicity in humans. However, a metabolite of styrene, styrene oxide, is carcinogenic. Treatment of over-exposure is symptomatic. Activated charcoal would be preferred in case of poisoning.

CONCLUSION: Are food contained in polystyrene foam safe? Yes, they are since systemic absorption of polymers is almost impossible. Polystyrene meets stringent FDA standards for use in food packaging and is safe. However, in circumstances when small amounts of styrene are present, some sensitive persons may develop transient mild reactions including GI irritation, nausea, vomiting, and fatigue. Can we get cancer from using foam containers? Very unlikely.

QUESTION: Anh Quang, trong danh sach 18 hoa chat bao quan thuc pham (preservative) cua Vietnam co potassium nitrate (salpetre) va sodium nitrate voi luong 500mg/Kg . Toi nho co mot bai nao do bao nitrate co the sinh goc NO 2 gay mutation co the tao ra ung thu. Anh vui long cho biet ly thuyet do neu co co dung khong va voi luong dung khong qua 500mg/Kg co the gay tac dung do khong. Hien nay ky nghe lam thuc pham cua nguoi Vn ke ca vung Little Saigon deu tieu thu rat nhieu nitrate chu khong phai nitrite. xin cam on anh. Le-van-Nhan

ANSWER: Both potassium nitrate and sodium nitrate are no more toxic than other neutral salts, and are absorbed rapidly and excreted unchanged, causing few reactions other than diuresis and perhaps catharsis. Acute toxicity of nitrate occurs as a result of reduction to nitrite, a process that can occur under specific conditions in the stomach or by bacteria in the GI tract. So the toxicity of K+ or Na+ nitrate is due to its conversion to nitrite. Symptoms of nitrite poisoning include methemoglobin formation, cyanosis, decreased blood pressure, headache, palpitations, flushed skin, nausea and vomiting, muscular weakness, incoordination, and death due to circulatory collapse. It should be noted that cyanosis due to methemoglobinemia does not respond to oxygen therapy (use IV methylene blue instead). In addition to reduced hemoglobin, prolonged administration of nitrates has been reported to affect glycolysis, the pentose phosphate cycle, and the activity of the glutathione-ascorbic acid system. The toxic dose of potassium nitrate varies greatly; from 15 to 30 grams may prove fatal but much larger doses have been taken without serious effects. The lethal dose of potassium nitrate is documented as 54 to 462 mg/kg of body weight. The probable oral lethal dose (human) of sodium nitrate is between 500 mg to 5000 mg/kg body weight. In mutation assays using cell cultures (Chinese Hamster Ovary cells) both nitrate and nitrite produce positive chromosomal aberration effects. Finally, sodium nitrite has shown a potential for carcinogenicity in laboratoty animals. In summary, nitrate salts are toxic only when they are not promptly absorbed due to their conversion to nitrite. Whether or not nitrate is properly absorbed varies with individual's existing pathological and anatomical condition.