Morpholine.

Also known as Diethyleneimide Oxide and 4-Oxazine. Morpholine is a synthetic liquid used as an ingredient in optical brighteners, as a solvent, and as an emulsifier in the process of waxing fruits and vegetables. Industrial uses include the production of rubber chemicals and for corrosion protection in nuclear power plant steam systems. At home, you may just find it in cleaning products as an 'optical brightener'.

Fruit tested was found to have residue rates of 2-6 parts per million on waxed apples where morpholine was the carrier. OSHA requires a full faceplate respirator when exposure potential can be 20 ppm or more. That's only about 4-5 apples! Morpholine has been banned in the European Union in waxing food products because it is known to be a precursor of N-nitrosomorpholine, a known carcinogen.

The hazard summary of the MSDS for Morpholine classifies it as a 3=serious hazard for health and flammability. The MSDS also states it is a corrosive chemical that can cause irritation and burning to the skin and eyes with possible eye damage. Other health concerns are irritation to the nose, throat and lungs, can be absorbed through skin, hazardous when inhaled, and may cause live and kidney damage. Repeated exposure can cause bronchitis, shortness of breath, coughing and wheezing.

Exposure to 1400 ppm is immediately dangerous to life and health.