1. Growth Regulators & Plant Hormones
Summon Chomchai, MD

2. Growth regulator & plant hormone:
Growth regulator : noun Date: 1936 : any of various synthetic or naturally occurring plant substances (as an auxin or gibberellin) that regulate growth
Plant hormone : noun Date: 1935 : an organic substance other than a nutrient that in minute amounts modifies a plant physiological process; especially : one produced by a plant and active elsewhere than at the site of production
Merriam-Webster Online Dictionary

3. Growth regulators & Plant hormones in Thailand
Hydrogen cyanamide
Ethephon
Cyclocel
Thiourea
Naphylene-1-acetic acid
Gibberellic acids

4. Hydrogen cyanamide (Dormex®)
The only hazardous growth regulator reported on MEDLINE!!!
Stimulates bud breaking after dormancy
Applied by spraying
Mode of exposure: skin and inhalation

5. Hydrogen cyanamide Mode of exposure: skin and inhalation
Inhibits aldehyde dehydrogenase (disulfiram-like effects)
Causes acetaldehyde syndrome when exposure coincided with alcohols

6. Hydrogen cyanamide
23 cases reported from Italy (MMWR October 5, 2001)
22 cases from occupational exposure: mixing & applying
1 unintentional ingestion
PPE status was unknown

7. Hydrogen cyanamide Eye and respiratory tract irritation Skin symptoms
Systemic symptoms: tachycardia, palpitation, headache, dizziness, weakness, nausea and vomiting, dyspnea, hypotension
12 workers were hospitalized

8. Cyanamide: other potential health risks
Contact dermatitis
Hepatitis and liver failure
Aplastic anemia/ agranulocytosis
Disulfiram-like effects

9. Surveillance for hydrogen cyanamide
Skin symptoms and signs
Complete blood count
Liver function test
Other symptoms

10. Cyanamide: control of exposure
Personal protective equipment
Chemical-resistant suit
Chemical-resistant gloves
Chemical-resistant footwear
Eye and face protection
Respirator with organic vapor removing cartridge

11. Ethephon Enhances releasing of ethylene by plants and fruits
fruit ripening
flower induction
stem elongation
stimulate latex flow in rubber)
Applied by dipping or spraying

12. Ethephon: health effects
Exposure: dermal or inhalation
Eye irritation; corneal erosion
Severe skin burns; may result in contractures
Lower respiratory tract irritation: bronchospasm, pneumonitis, pulmonary edema

13. Ethephon Decontamination & supportive care, no specific treatment
Protection: Personal protective equipment
Chemical-resistant suit
Chemical-resistant gloves
Chemical-resistant footwear
Eye and face protection
Respirator with organic vapor removing cartridge

14. Cyclocel (Chlormequat)
Prevents premature fruit drop in oranges and mangos
Increases yields in wheat
Promotes lateral branching and flowering in geraniums

15. Cyclocel (Chlormequat)
Dermal contact of dust and sprays, especially during application
Contact dermatitis
Supportive care/ no specific treatment
Protection: Protective clothing and gloves

16. Thiourea Stimulates sprouting from dormant tubers
Dermal exposure upon mixing and application
Irritant contact dermatitis / photo-contact dermatitis (rubber industry/ silver & copper cleaners)
Supportive care/ no specific treatment
Protection: Protective clothing and gloves

17. NAPHTHALENE-1-ACETIC ACID
Stimulates root formation
Prevents premature fruit drop in apples, mangoes, watermelons, pineapples, cucumbers, cotton, soya
Controls regrowth of tree sprouts after trimming of lemon, pomegranate
Inhibits sprouting in stored potato, ornamental bulbs
Application: dipping or spraying

18. NAPHTHALENE-1-ACETIC ACID
Expoure though inhalation during application
Nasal irritation
Supportive care, no specific treatment

19. Gibberellic acids No health hazard of gibberellic acids reported
Prevention: avoid contact with the chemical, wash splash from skin immediately

20. Conclusion
Most of growth regulators and plant hormones are relatively benign.
Researches on health hazards of growth regulators and plant hormones