Explanation:
Toxicity
Ethephon is corrosive in acute dermal irritation studies using rabbits,
has the potential to cause eye irritation, and has been placed in Toxicity
Category I (the highest of four categories) for these effects. It is moderately
acutely toxic by the oral, dermal and inhalation routes (Toxicity Category
III), and does not cause skin sensitization.
An organophosphate pesticide, ethephon caused plasma cholinesterase
inhibition in a 16-day oral human study and clinical signs of toxicity in a
second study. In a dermal toxicity study using rabbits, skin effects were
observed at all doses.
In a combined chronic/oncogenicity study using rats, plasma and
erythrocyte cholinesterase were inhibited at all doses. At the highest dose
levels, ethephon caused body weight decrease and kidney effects, but no
carcinogenic effects were observed. In a cancer study using mice, no
evidence of treatment related tumors was observed. Ethephon has been
classified as a Group D carcinogen based on "the insufficiency of the weight
of evidence" regarding its cancer-causing potential.
One chronic toxicity study using beagle dogs caused plasma
cholinesterase inhibition at all doses, and smooth muscle atrophy in the gut.
In a second beagle dog study, treatment related effects included decreased
spleen and body weight plus decreased hemoglobin and hematocrit in the
males.
Developmental toxicity studies using rats and rabbits show no
evidence of a potential for developmental effects at doses that are not toxic
to the mother. In a reproductive toxicity study using rats, administration of
the test compound caused decreased survival in the offspring and decreased
body weight gain in adult females, but no effects on fertility, gestation,
mating, organ weights, or histopathology in any generation.
Ethephon was positive in one mutagenicity study and negative in two
others. It does not appear to cause delayed neurotoxicity based on a study
using hens, however studies using mammals are now required as
confirmatory data.
Human poisoning incidents involving ethephon include four cases of
skin injury (irritation) in California as a result of exposure to field residues,
one possible systemic poisoning case, and 29 telephone calls to the National
Pesticides Telecommunications Network reporting eye and skin irritation
from misuse of ethephon, sometimes in combination with other pesticides.
Dietary Exposure
People may be exposed to residues of ethephon through the diet.
Tolerances or maximum residue limits have been established for ethephon in
many raw agricultural commodities, processed foods, and feed. Please see
40 CFR 180.300(a) and (b), 185.2700(a), (b) and (c), and 186.2700(a).
