Health Hazard Assessment of Morpholine in Wax Coatings of Apples

Why are wax coatings used on some fruits and vegetables? Are they safe? Many fruits and vegetables make their own natural waxy coating to help retain moisture because most produce is 80 to 95 percent water. After harvest, but before the produce is paJul 15, 08 Morpholine is a solvent and emulsifier used in the preparation of wax coatings for fruits and vegetables. In the presence of excess nitrite, formed mainly from naturally-occurring nitrate in the diet, morpholine can be chemically modified (nitrosated) to form N-nitrosomorpholine (NMOR), a genotoxic carcinogen in rodents.

While morpholine alone does not appear to pose a health concern, the main issue is whether sufficient NMOR can be produced by humans upon ingestion, to pose a health risk. Morpholine itself is neither a carcinogen nor a teratogen and does not cause chronic toxicity in rats and mice. Based on a no observed adverse effect level (NOAEL) in a chronic oral toxicity study and several safety factors, an acceptable daily intake (ADI) of 0.48 mg/kg bw/day was estimated. When not considering the potential for nitrosation, the respective morpholine exposure for children and adults is about 8% and 5% of the ADI, and not a cause for concern. In studies conducted in experimental animals it has been determined that the formation of NMOR is dependent on the administration of sufficiently large doses of morpholine and nitrite.

Under these specific conditions, rats fed morpholine and nitrite develop hepatocellular carcinoma (cancer of the liver), presumably due to the formation of NMOR. Although it is often assumed that there is some probability of harm at any level of exposure to a genotoxic carcinogen, actual exposure may be so low that the health risk is essentially negligible. Extrapolation of rat tumour data was used to estimate a safe dose in humans (4.3 ng/kg bw/day). Regarding the presence of NMOR on apples coated with wax containing morpholine: No NMOR was determined to be present on these apples, and no NMOR was formed when morpholine and nitrite were combined in experiments conducted in the presence of apple flesh.

The possibility that morpholine might be nitrosated by humans to form NMOR during digestion was investigated. Since there is no direct human data on the nitrosation rate of morpholine to NMOR, this was estimated indirectly. The inhibitory effects of antioxidants present in apple were also considered. From the estimated morpholine exposure, the possible endogenously formed NMOR was estimated to be 2.2 and 3.6 ng/kg bw/day for adults and children, respectively. This possible exposure to NMOR derived from morpholine on waxed apples is less than the above estimated safe dose of 4.3 ng/kg bw/day. Uncertainties in this estimate of NMOR formation include the physiological differences between humans and rats, and actual levels of nitrite consumed.

It is unlikely that these uncertainties would increase the estimated NMOR formation. Waxes are applied in order to: help retain moisture in fruits and vegetables during shipping and marketing; help inhibit mold growth; protect fruits and vegetables from bruising; prevent other physical damage and disease; enhance appearance. By protecting against moisture loss and contamination, wax coatings help fresh fruits and vegetables maintain wholesomeness and freshness. Waxing does not improve the quality of any inferior fruit or vegetables; rather, waxing — along with proper handling — contributes to maintaining a healthful product.

Waxes by themselves do not control decay; rather, they may be combined with some chemicals to prevent the growth of mold. The Food and Drug Administration and the Environmental Protection Agency strictly regulate the safety and use of these substances. Waxes are also used on candies, pastries and gum and come from natural sources. Wax sources generally are plants, food-grade petroleum products or insects (similar to honey from bees). Some waxes can be made from dairy or animal sources, but we are not aware of any such coatings being used on fruits and vegetables in this country.

This is particularly important for people following Kosher or vegetarian diets and who don’t want any animal-based wax on their produce. Any commodities that do have this type of coating must be labeled "Coated with animal-based wax." Waxes are used only in tiny amounts. In fact, each piece of waxed fruit only has a drop or two of wax. Waxes may be mixed with water or other wetting agents to ensure they are applied thinly and evenly. The government regulates wax coatings to ensure their safety. Coatings used on fruits and vegetables must meet the food additive regulations of the U.S. Food and Drug Administration.

Extensive research by governmental and scientific authorities has shown that approved waxes are safe to eat. Waxes are indigestible, which means they go through the body without breaking down or being absorbed. Produce shippers and supermarkets are required by federal law to label produce items that have been waxed so you will know whether the fruits and vegetables you buy are coated. Consumers will see signs in produce departments that say "Coated with food-grade vegetable-, petroleum-, beeswax-, and/or shellac-based wax or resin, to maintain freshness." None of these coatings are animal-based, and they all come from natural sources. Any consumers who have questions about wax coatings should talk to their grocers. Waxes may turn white on the surface of fruits or vegetables if they have been subjected to excessive heat and/or moisture.

This whitening is safe and is similar to that of a candy bar that has been in the freezer. Consumers do have choices. Waxes generally cannot be removed by regular washing. If consumers prefer not to consume waxes — even though the waxes are safe — they can buy unwaxed commodities or can peel the fruit or vegetable, thereby removing any coating. Commodities that may have coatings applied include apples, avocados, bell peppers, cantaloupes, cucumbers, eggplants, grapefruits, lemons, limes, melons, oranges, parsnips, passion fruit, peaches, pineapples, pumpkins, rutabagas, squash, sweet potatoes, tomatoes, turnips and yucca. However, they are not always waxed.