Growth Regulators & Plant Hormones Summon Chomchai, MD Toxbuster@hotmail.com

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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