Toxicological and Ecotoxicological Investigations of Liquid Crystals

Since the beginning of the activities in the LCD field com-prehensive toxicological and ecotoxicological investigations of liquid crystals were carried out following the precautionary principle. The results can be summarized as follows:

1. Liquid crystals are not acutely toxic.
2. A few may be irritant, corrosive or sensitising, but effects can be avoided by concentration limitation in mixtures.
3. Liquid crystals are not mutagenic or genotoxic in bacteria (Ames-Test) and in mammalian cells (Mouse Lymphoma Assay or Chromosome aberration test).
4. Liquid crystals are not suspicious of carcinogenicity.
5. They are not harmful to aquatic organisms (bacteria, algae, daphnia, fish).
6. They do not possess a significant bioaccumulation potential.
7. Some are not readily biodegradable.

These statements do not only apply for the liquid crystals of the Merck KGaA but also for those of the two main competitors Chisso Corporation and Dainippon Ink & Chemicals. All 3 manufacturers supplying much over 90 % of the world market have committed themselves not to introduce acutely toxic or mutagenic liquid crystals into the market. The remaining liquid crystals, mainly manufactured in China, are older patent-free substances of the 3 big manufacturers and also covered by their investigations. Hence, these also can be considered non-hazardous.

Despite the high chemical stability of liquid crystals, which is a prerequisite for their application in liquid crystal displays, liquid crystals do not fulfill the POP criteria (persistent organic pollutants) as laid down in the Stockholm convention on POPs, because liquid crystals are neither acutely toxic nor bioaccumulating (BCF <5000).