Pesticides for Stored Products
243
Ethylene dibromide is another important fumigant. It has a boiling point of
13 1. 6°C; this relatively high boiling point makes it useful for fumigation in
tropical climates. It has been used in the U.S. for fumigation of citrus and other
fruits, but it does not penetrate wheat well, and high residues remain in the
surface layers. Ethylene dibromide is not very reactive, but some ethylene glycol
is formed in wheat on heating. It is highly sorbed, and the low rate of desorption
on airing may result in unchanged residual fumigant. When grain treated with
ethylene dibromide was fed to hens, their egg-laying capacity was affected (Bierer
and Vickers, 1959), and degeneration of spermatazoa occurred in bulls fed with
ethylene-dibromide-treated corn (Amir and Volcani, 1965). Treated feeds do not
produce symptoms of chronic toxicity in rats (Alumot et al., 1974), but 13hydroxyethyl derivatives of glutathione were isolated from the rats' livers (Nachtomi, 1970). It has been recognized that spermatogenesis in humans is affected
by ethylene bromide. It is a mutagen, and 0.15--0.8 mlIanimal per day fed to
rats or mice by chronic oral intubation caused a high incidence of carcinomas
of the stomach after 10 weeks (Olson et al., 1973). The related compound
dibromochloropropane (a soil fumigant) also caused carcinomas in rats.
Phosphine, another major fumigant in the stored food and beverage industry,
boils at - 87°C. Although it is flammable and toxic, its use as a fumigant is
increasing because it can be conveniently generated from tablets containing
aluminum phosphide and ammonium carbamate (Phostoxin®), and it appears to
present little long-term hazard. Residues are quite low, and the phosphoruscontaining residue is mainly phosphite and hypophosphite.
Ethylene oxide and propylene oxide are toxic to microorganisms as well
as to insects. They are quite reactive; ethylene oxide may react by nucleophilic
ring fission to give low-molecular-weight derivatives or addition products such
as ethylene chlorohydrin, ethylene bromohydrin, or ethylene glycol. It also may
react with functional groups in constituents of food or commodities to give the
c.Jrresponding hydroxyethylated compounds of, for example, sugars and amino
acids.
Most conventional fumigants contain reactive halogen atoms and are capable
of alkylation reactions; ethylene oxide is also a reactive nucleophilic molecule.
Nevertheless, in the quantities recommended for fumigation, these compounds
are expected to produce little change in the flavor, processing qualities, or nutrient
quality of the commodity, although detection of subtle changes in nutrient quality
requires more careful and long-term feeding studies.
A major concern is that residues of fumigants may have long-term toxicological implications and may, in some subtle way, affect processes that regulate
cell division. Methods of analysis based on inorganic bromide are no longer
satisfactory as a basis for setting tolerances for brominated fumigants, and sophisticated analytical methods are important to ensure that residues of unchanged
243
Ethylene dibromide is another important fumigant. It has a boiling point of
13 1. 6°C; this relatively high boiling point makes it useful for fumigation in
tropical climates. It has been used in the U.S. for fumigation of citrus and other
fruits, but it does not penetrate wheat well, and high residues remain in the
surface layers. Ethylene dibromide is not very reactive, but some ethylene glycol
is formed in wheat on heating. It is highly sorbed, and the low rate of desorption
on airing may result in unchanged residual fumigant. When grain treated with
ethylene dibromide was fed to hens, their egg-laying capacity was affected (Bierer
and Vickers, 1959), and degeneration of spermatazoa occurred in bulls fed with
ethylene-dibromide-treated corn (Amir and Volcani, 1965). Treated feeds do not
produce symptoms of chronic toxicity in rats (Alumot et al., 1974), but 13hydroxyethyl derivatives of glutathione were isolated from the rats' livers (Nachtomi, 1970). It has been recognized that spermatogenesis in humans is affected
by ethylene bromide. It is a mutagen, and 0.15--0.8 mlIanimal per day fed to
rats or mice by chronic oral intubation caused a high incidence of carcinomas
of the stomach after 10 weeks (Olson et al., 1973). The related compound
dibromochloropropane (a soil fumigant) also caused carcinomas in rats.
Phosphine, another major fumigant in the stored food and beverage industry,
boils at - 87°C. Although it is flammable and toxic, its use as a fumigant is
increasing because it can be conveniently generated from tablets containing
aluminum phosphide and ammonium carbamate (Phostoxin®), and it appears to
present little long-term hazard. Residues are quite low, and the phosphoruscontaining residue is mainly phosphite and hypophosphite.
Ethylene oxide and propylene oxide are toxic to microorganisms as well
as to insects. They are quite reactive; ethylene oxide may react by nucleophilic
ring fission to give low-molecular-weight derivatives or addition products such
as ethylene chlorohydrin, ethylene bromohydrin, or ethylene glycol. It also may
react with functional groups in constituents of food or commodities to give the
c.Jrresponding hydroxyethylated compounds of, for example, sugars and amino
acids.
Most conventional fumigants contain reactive halogen atoms and are capable
of alkylation reactions; ethylene oxide is also a reactive nucleophilic molecule.
Nevertheless, in the quantities recommended for fumigation, these compounds
are expected to produce little change in the flavor, processing qualities, or nutrient
quality of the commodity, although detection of subtle changes in nutrient quality
requires more careful and long-term feeding studies.
A major concern is that residues of fumigants may have long-term toxicological implications and may, in some subtle way, affect processes that regulate
cell division. Methods of analysis based on inorganic bromide are no longer
satisfactory as a basis for setting tolerances for brominated fumigants, and sophisticated analytical methods are important to ensure that residues of unchanged