This field observation prompted several research studies about environmental and
mesocosm models focused on the assessment of pyrethroids and other pesticides
[1]. As a consequence, some regulation agencies came into existence. In 1970, the
Environmental Protection Agency (EPA) was founded. From that moment on, the
use of organochlorinated compounds was restricted or banned as they were considered toxic and contaminant [2, 3]. Nevertheless, they are still allowed to fight malaria
[4–6].
In the 1940s, it was discovered that many organophosphate compounds had
unique properties for the protection of plants – and that the most volatile and toxic
could be used as chemical weapons. However, not until the 1960s did organophosphate compounds become popular. At the end of the same decade, there was an
increasing interest in carbamate pesticides.
Organophosphates and carbamates had simple structures, and it was easy to
synthesise analogous derivatives. They also showed some advantages over
organochlorinated pesticides [1]. They were selectively toxic with different effects
depending on the species; they affected insects more than mammals [7]; the effects
on mammals occurred mostly after intense exposition rather than accumulation; they
were more biodegradable, therefore, less persistent, and they allowed the creation of
compounds that stay inside the plants for a few weeks and protect them. On the other
hand, regulations and bans on the use of organophosphates and carbamates emerged
as a consequence of new data on their actual toxicity [8]. Toxicology studies are a
key element of the development of new pesticides nowadays.
In the 1970s, pyrethroids stopped being mere household products to become pest
control agents in agriculture. Moreover, in the last couple of decades, pyrethroids
have replaced organophosphate pesticides in most of their applications the same way
the latter had replaced organochlorinated pesticides before [9, 10]. Pyrethroids were
very effective.
Works on the optimisation of these derivatives from pyrethrin had been going on
for decades, and several improvements were achieved [1]. Their photostability was
improved without compromising their biodegradability. They achieved a selective
toxicity and metabolic routes of degradation – that were different for cis and trans
isomers. They were produced as fumigants as well as soil pesticides. And they were
made more powerful so that smaller amounts would need to be used and environmental contamination would be reduced.
The development of pyrethroids included some aspects that helped reduce the
impact of pesticides on the environment: higher effectiveness implying smaller
amounts of product needed, selective toxicity, concern on the occurrence of pesticides in the environment and replacement of persistent compounds with degradable
compounds [1].
Introduction to Pyrethroid Insecticides: Chemical Structures, Properties, Mode. . .
3
mesocosm models focused on the assessment of pyrethroids and other pesticides
[1]. As a consequence, some regulation agencies came into existence. In 1970, the
Environmental Protection Agency (EPA) was founded. From that moment on, the
use of organochlorinated compounds was restricted or banned as they were considered toxic and contaminant [2, 3]. Nevertheless, they are still allowed to fight malaria
[4–6].
In the 1940s, it was discovered that many organophosphate compounds had
unique properties for the protection of plants – and that the most volatile and toxic
could be used as chemical weapons. However, not until the 1960s did organophosphate compounds become popular. At the end of the same decade, there was an
increasing interest in carbamate pesticides.
Organophosphates and carbamates had simple structures, and it was easy to
synthesise analogous derivatives. They also showed some advantages over
organochlorinated pesticides [1]. They were selectively toxic with different effects
depending on the species; they affected insects more than mammals [7]; the effects
on mammals occurred mostly after intense exposition rather than accumulation; they
were more biodegradable, therefore, less persistent, and they allowed the creation of
compounds that stay inside the plants for a few weeks and protect them. On the other
hand, regulations and bans on the use of organophosphates and carbamates emerged
as a consequence of new data on their actual toxicity [8]. Toxicology studies are a
key element of the development of new pesticides nowadays.
In the 1970s, pyrethroids stopped being mere household products to become pest
control agents in agriculture. Moreover, in the last couple of decades, pyrethroids
have replaced organophosphate pesticides in most of their applications the same way
the latter had replaced organochlorinated pesticides before [9, 10]. Pyrethroids were
very effective.
Works on the optimisation of these derivatives from pyrethrin had been going on
for decades, and several improvements were achieved [1]. Their photostability was
improved without compromising their biodegradability. They achieved a selective
toxicity and metabolic routes of degradation – that were different for cis and trans
isomers. They were produced as fumigants as well as soil pesticides. And they were
made more powerful so that smaller amounts would need to be used and environmental contamination would be reduced.
The development of pyrethroids included some aspects that helped reduce the
impact of pesticides on the environment: higher effectiveness implying smaller
amounts of product needed, selective toxicity, concern on the occurrence of pesticides in the environment and replacement of persistent compounds with degradable
compounds [1].
Introduction to Pyrethroid Insecticides: Chemical Structures, Properties, Mode. . .
3