Merck Chemicals - Safety of LC Materials

Safety of LC Materials: Toxicological and Eco-Toxicological Investigations

Dr. Werner Becker, Liquid Crystals Division / Technology & Regulatory AffairsMDT Workshop “Responsible Care and Legal Compliance”, 15th Oct. 2008

2Safety of LC Materials: Toxicological and Ecotoxicol. InvestigationsDr. Werner Becker, Merck KGaA, LC T & RA MDT Workshop 15th Oct. 2008

• Self-commitment and statement of the 3 majorLC manufacturers

• Design of toxicological studies and test strategy for liquid crystals

• Short term toxicity of LCs • Mutagenicity of LCs• Ecotoxicological properties of LCs• Conclusions

Presentation Outline


Merck KGaA has committed itself to not introduce into the market liquid crystal materials which are either acutely toxic or mutagenic.

Likewise Chisso Corp. and Dainippon Ink have committed themselves, too.

Self-Commitment


Statement on the Safety of Liquid Crystal Materials

We, the three liquid crystal material suppliers: Merck, Chisso and Dainippon Ink maintain the safety of our products, both towards the users and the environment.

Therefore, we carry out intensive toxicological investigations and do not introduce the acutely toxic or mutagenic liquid crystal materials into the market.

Moreover, we investigate the ecotoxicological properties of our liquid crystal materials in compliance with legal regulations and as precautionary measures according to the principles of " Responsible Care " and " Product Stewardship ".

Merck KGaA:

Mr. Walter GalinatExecutive Vice PresidentLiquid Crystals Division

Chisso Corporation:

Dr. Yasuyuki Goto,Executive Officer & General Manager,Liquid Crystals Division

Dainippon Ink and Chemicals:

Dr. Haruyoshi Takatsu,General Manager, R&D


Design of the Toxicological Studies

Studies are performed:

• during the development of the liquid crystal compounds (i.e. before introduction into the market), bacteria mutagenicity evenbefore sampling to customers

• without legal obligation

• according to international guidelines (OECD, EU, MITI)

• in compliance with Good Laboratory Practice-Standards

• following the European and national regulations for animal welfare

• including analogy considerations (Homologous Series Strategy)


Homologous Series Strategy

Homologous series of liquid crystals (CCP-n0CF3):

H

HOCF3

alkyl side chain core structure terminalsubstituent

• Homologous compounds have:- the same core structure and terminal substituent- only differ in the length of the alkyl side chain

• Homologue with shortest chain length exhibits most pronounced toxicity.

⇒ Toxicity studies are performed with homologue with shortest side chain.

⇒ These results can be applied to other homologues of the series.


Institute of Toxicology, Darmstadt



• Self-commitment and statement of the 3 majorLC manufacturers

• Design of toxicological studies and test strategy for liquid crystals

• Short term toxicity of LCs • Mutagenicity of LCs• Ecotoxicological properties of LCs• Conclusions



Acute Toxicity Testing(Acute Toxic Class Method OECD 423)

• Test species: rats (3 per sex and dose)• Route of administration: oral• Dose: max. 2000 mg/kg body weight• Observation period: 14 days• Effects recorded: death and all other

signs of toxicity

• Classification and labelling according to themedian lethal dose (LD50)

• LD50: statistical value,indicates the substance amount at which50 % of the test animals are considered to die

Test animal: rat


Acute Oral Toxicity of Liquid Crystals

260 LCs and 14 mixtures caused no effects

8 LCs are classified as harmful- only old STN/TN substances concerned, none of the TFT singles→ concentration in mixtures < 10% LC mixtures are not harmful

1 LC was found to be toxic

→ excluded from further development and not introduced into the market

no marketed LC is acutely toxic and no TFT LC is even harmful !

LCs LC-mixturesNo. of substances tested: 269 14no effect (LD50 > 2000 mg/kg bw) 260 14harmful (LD50 200 - 2000 mg/kg bw) 8 0

Status:Sept. 23, 2008


• Self-commitment and statement of the 3 major LC manufacturers

• Design of toxicological studies and test strategy forliquid crystals

• Short term toxicity of LCs • Mutagenicity of LCs

• Bacteria mutagenicity (Ames test)• Mammalian mutagenicity (Chromosome

Aberration)• Ecotoxicological properties of LCs• Conclusions



Mutation: What is a Mutation ?

Mutation is the critical event in the initiation of cancer

Cell with nucleusDNA molecule

Mutagenic substances can cause DNA damagein the organic purine (guanine, adenine) and pyrimidine (thymine, cytosine) bases


Principle of the Bacterial Mutagenicity Assay (Ames-Test OECD 471, 473)

Mutant bacteria:Salmonella typhimurium (his-) and/or

Escherichia coli (trp-)

treatment with test substance (TS)

+/- metabolic activation (S9)

TS is not mutagenic (his-/trp-):no backmutation to wildtype bacteria

no revertant bacterial coloniesin his-free and/or trp-free media

TS is mutagenic (his+/trp+):backmutation to wildtype bacteria

revertant bacterial coloniesin his-free and/or trp-free media


Mutagenic Potential of LCs in Bacteria

276 LC compounds and 14 mixtures investigated arenot mutagenic in bacteria

2 LCs were mutagenic in bacteria and were not furtherdeveloped and not introduced into the market

no marketed LC is mutagenic !

LCs LC-mixtures

No. of LCs studied: 278 14

not mutagenic: 276 14



Principle of the Chromosome Aberration Test (OECD 476)

Cells from Chinese Hamster Lung (CHL) or Ovary (CHO)

treatment with test substance (TS)

expression period

+/- metabolic activation S9

TS is not clastogenic:No Chromosome Aberrations

TS is clastogenic:Chromosome Aberrations


Clastogenic Potential of LCs in Mammalian cells

• Several chromosome aberration studies were performedfor notification purposes

no LC compound is clastogenic in mammalian cellsno indication for a carcinogenic potential of LCs

Number of LCs studied: 46

not clastogenic: 46Status:Sept. 25, 2008


• Self-commitment and statement of the 3 major LC manufacturers

• Design of toxicological studies and test strategy forliquid crystals

• Short term toxicity of LCs • Mutagenicity of LCs• Ecotoxicological properties of LCs

• Aquatic toxicity (algae, fish, daphnia)• Biodegradation• Bioaccumulation (Bioconcentration)

• Conclusions



Aquatic Test Organisms

unicellular green algae(Desmodesmus subspicatus)Zebra fish

(Danio rerio)

Water flea(Daphnia magna)

Length: up to 5 cm

Size: up to 5 mm


Aquatic Toxicity of Liquid Crystals

• LCs are poorly water soluble and difficult to test in aquatic systems

• Available tests- fish: 7 LCs

- daphnia: 39 LCs (+ 1 mixture)

- algae: 13 LCs (+ 1 mixture)

- bacteria: 8 LCs

ResultsNo effects up to the highest recommended test substance concentration(100 mg/L) for aquatic organisms

Liquid Crystals are not harmful to aquatic organisms !

Daphnia magnaGreen algae



Biodegradation

Activated sludge

Amoeba

Bacteria


Ready Biodegradability of Liquid Crystals

Liquid crystals (in particular SFM compounds) are chemically very stable and not readily biodegradable.

Degradation rates were between 0 and 55 % after 28 days.

Ester type substances and CN substituted compounds are partly biodegradable whereas SFM compounds are not

Substances tested to date : 89



• Guideline: Japanese Guideline

• Test species: Japanese rice fish

• Duration: - Uptake phase: 28 days (can be extended to up to 60 days)

- Depuration phase

• Analysis of test substance concentration in water and fish

• Results are given as Bioconcentration factor (BCF)

For notification purposes, 46 LCs were tested for bioaccumulation

Conclusion: Liquid Crystals do not show a significantbioaccumulation potential !

Bioaccumulation (Bioconcentration)

waterinsubstancetestofionconcentratm equilibriufishinsubstancetestofionconcentratm equilibriu

BCF =

(Medaka, Oryzias latipes)


Summary of Toxicological and Eco-toxicological Testing Results

Commercial liquid crystal compounds

are not acutely toxic,are not mutagenic in bacteria (Ames-Test), are not clastogenic in the chromosome aberration test in mammalian cells,are not suspicious of carcinogenicity,are not harmful to aquatic organisms (bacteria, algae, daphnia, fish),do not show a significant bioaccumulation potential, but are not readily biodegradable.


All things are poison; there isnothing that is not a poison; only the dose makes that a thing is not a poison.

Paracelsus (1493-1541)

What is a Poison ?


Thank you for your attention !