11.5 Impact on Science and Society
The principle of chirality and its relevance to pharmacology, medicine and chemistry
is well recognised. The continuously growing impact of chiral pollutants on the
environment has increased the interest of scientists in the chiral pollutants. The use
of pesticides is increasing continuously to meet the food demand of the overgrowing
world population. Furthermore, chiral pollutants may metabolise stereoselectively in
the biological environment. One of the enantiomers may be bio-transformed in the
environment while the other may not. This may result in the selective enrichment of
one of the enantiomers. For example, one enantiomer of a pesticide is estrogenic and
the other is not. In some cases, both enantiomers bind hormone receptors equally, but
each shows diverse receptor-mediated responses. Therefore, the enantiomers have
different toxic effects on the animals. For example, R-enantiomers of dichlorprop,
mecoprop and phenoxypropionic acid herbicides are active to kill the weeds, while
the S-enantiomers are inactive thus leading to unnecessary pollution loads and
toxicities in the environment (Williams 1996).
Scientists have been studying enantiomer-specific effects of the chiral pollutants
for a long time. Zhang et al. (2013) reviewed the enantiomer-specific environmental
transformation, transportation, bioaccumulation and toxic effects of chiral pollutants. The authors reported enantiomeric fraction (EF) values for chiral pollutants in
the order of soil > water >air. In animals, the EF deviation was also observed with
highest values in the brain followed by liver. It may be due to enantiomer-specific
biological processes viz. uptake, binding, transformation and clearance in the organisms. Scientists at the Ecosystem Research Division of NERL/ORD in Athens are
studying the phenomenon of chirality of the pesticides and other chiral pollutants,
with emphasis on the impact of enantioselectivity and fate of the chiral pesticides.
Basically, chiral pollutants may exhibit enantiomer-specific acute and chronic
toxicities, as well as endocrine-disturbing capacities. The information on the
physico-chemical transformation of chiral pollutants in the presence of chiral compounds/catalysts is also an important aspect in ascertaining the enantioselective
toxicities. Therefore, the studies on the stereoselective transformation of chiral
pollutants may be used to ascertain the enantioselective toxicities. The regulating
authorities cannot formulate any guideline without knowing the true picture of the
risks and effects of the chiral pollutants. Unfortunately, there are no sufficient data
on the latter aspects of the chiral pollutants. Therefore, there is a great need to
develop a data repository for information on enantioselective synthesis, biotransformation, biodegradation, enzymatic uptake, clearance and toxicities of the chiral
pollutants.
Nowadays, human populations and the environment are exposed to a multitude of
environmental pollutants including chiral contaminants. There are many chiral
pollutants, which are hazardous and toxic for exposed individuals. Such chiral
pollutants often are transformed enantioselectively. Finally, these transformation
products reach exposed humans and can lead to hazardous effects. Animals and
plants including bacteria, fungi and algae may transform these chiral pollutants
312
11 Perspectives
The principle of chirality and its relevance to pharmacology, medicine and chemistry
is well recognised. The continuously growing impact of chiral pollutants on the
environment has increased the interest of scientists in the chiral pollutants. The use
of pesticides is increasing continuously to meet the food demand of the overgrowing
world population. Furthermore, chiral pollutants may metabolise stereoselectively in
the biological environment. One of the enantiomers may be bio-transformed in the
environment while the other may not. This may result in the selective enrichment of
one of the enantiomers. For example, one enantiomer of a pesticide is estrogenic and
the other is not. In some cases, both enantiomers bind hormone receptors equally, but
each shows diverse receptor-mediated responses. Therefore, the enantiomers have
different toxic effects on the animals. For example, R-enantiomers of dichlorprop,
mecoprop and phenoxypropionic acid herbicides are active to kill the weeds, while
the S-enantiomers are inactive thus leading to unnecessary pollution loads and
toxicities in the environment (Williams 1996).
Scientists have been studying enantiomer-specific effects of the chiral pollutants
for a long time. Zhang et al. (2013) reviewed the enantiomer-specific environmental
transformation, transportation, bioaccumulation and toxic effects of chiral pollutants. The authors reported enantiomeric fraction (EF) values for chiral pollutants in
the order of soil > water >air. In animals, the EF deviation was also observed with
highest values in the brain followed by liver. It may be due to enantiomer-specific
biological processes viz. uptake, binding, transformation and clearance in the organisms. Scientists at the Ecosystem Research Division of NERL/ORD in Athens are
studying the phenomenon of chirality of the pesticides and other chiral pollutants,
with emphasis on the impact of enantioselectivity and fate of the chiral pesticides.
Basically, chiral pollutants may exhibit enantiomer-specific acute and chronic
toxicities, as well as endocrine-disturbing capacities. The information on the
physico-chemical transformation of chiral pollutants in the presence of chiral compounds/catalysts is also an important aspect in ascertaining the enantioselective
toxicities. Therefore, the studies on the stereoselective transformation of chiral
pollutants may be used to ascertain the enantioselective toxicities. The regulating
authorities cannot formulate any guideline without knowing the true picture of the
risks and effects of the chiral pollutants. Unfortunately, there are no sufficient data
on the latter aspects of the chiral pollutants. Therefore, there is a great need to
develop a data repository for information on enantioselective synthesis, biotransformation, biodegradation, enzymatic uptake, clearance and toxicities of the chiral
pollutants.
Nowadays, human populations and the environment are exposed to a multitude of
environmental pollutants including chiral contaminants. There are many chiral
pollutants, which are hazardous and toxic for exposed individuals. Such chiral
pollutants often are transformed enantioselectively. Finally, these transformation
products reach exposed humans and can lead to hazardous effects. Animals and
plants including bacteria, fungi and algae may transform these chiral pollutants
312
11 Perspectives