Treated bed nets are safe to use

Treated bed nets are safe to use: study

For malaria, bed nets treated with insecticides offer an effective strategy in the fight against malaria.

A few weeks ago, an acquaintance in Wales in the United Kingdom, flagged an article on the Nation website that left me in shock.

It was about the safety of insecticide-treated bed nets. The article reported that researchers had said that pyrethroid insecticides used in mosquito nets could cause cancer and asthma in infants and children. 

The article started well by stating that high concentrations of synthetic insecticides are unsafe, but lost the plot by later implying that mosquito nets are unsafe because they have these chemicals. No chemical compound is completely safe for humans and especially at high doses, therefore, all individuals should minimise exposure to any insecticide and other chemical compounds in general.

However, the concentration of insecticides used to treat mosquito nets is highly regulated and bed net manufacturers follow guidelines set by the World Health Organisation’s Pesticide Evaluation Scheme (WHOPES) to reduce risk.

Moreover, the insecticide-treated mosquito nets used in homes have been evaluated for safety several times using rigorous scientific methods and processes.

For these insecticides to be considered very toxic, they have to be taken orally because absorption through the skin is very slow and only small quantities might be absorbed.

While it has been alleged before that pyrethroids and pyrethrins are carcinogenic, the evidence has not been conclusive and WHOPES notes the challenges involved in testing this epidemiologically.


Moreover, published literature and information from WHOPES states that “laboratory studies using animals have not revealed any carcinogenic hazard to humans,” therefore it has not warranted such a study.

Further, the article stated that scientists intend to use pyrethrins instead of pyrethroids, yet the natural crude pyrethrin extract is in fact more toxic than synthetic pyrethroids, because pyrethrins  have some compounds that increase allergic reactions that could be linked to asthma.

Therefore, pyrethrins must first be purified before use. It is also important to note that synthetic pyrethroids are similar to pyrethrins both in their chemical structure and mode of action. They both act in insects by interfering with transmission of signals in the insects’ nerves.

Humans and other mammals rapidly break down these compounds and that is why they generally do not have an effect on us. However, some individuals suffer from skin irritation upon contact with pyrethrins and in some cases more adverse effects such as dermatitis, conjunctivitis, rhinitis and asthma.

The article also alleged that some countries have banned the use of pyrethroids, but it failed to document these countries for our reference.

Fortunately, KEMRI and even the National Malaria Control Programme manager, set the record straight by reiterating that the concentration of insecticides used in mosquito nets is  safe for humans.

The problem with such an article, apart from the fact that it did not give the public enough information about the insecticides, is that without proper scrutiny, readers might reject the use of insecticide-treated mosquito nets and thus put a dent on the momentum to control and eliminate malaria.

The consequence might be an upsurge of malaria cases with significant implications for the control of malaria not only in Kenya but in Sub-Saharan Africa and the world. Similar miscommunication led to outbreaks of measles in the United Kingdom after reports emerged claiming that the measles vaccine was not safe.


Malaria is a real disease that has severe effects including death, if left untreated, or if medical care is sought very late, thus we must protect ourselves from mosquito bites.

With this in mind, journalists and scientists must understand each other to avoid miscommunication, which can have dire effects.

The bigger story is that scientists are using nanotechnology to develop pyrethrins to push back against the threat of insecticide resistance in mosquitoes. As mosquitoes become more resistant to insecticides, new chemicals will be needed and WHO encourages the development of new insecticides.

The major challenge in public health disease control is the availability of cheap and easily available tools to control diseases. For malaria, bed nets treated with insecticides offer an effective strategy in the fight against malaria.

 I, therefore, echo the WHO call to scale up the use of insecticide-treated bed nets to control malaria. Current scientific evidence and the WHO says that pyrethroids used in bed nets are safe, and everyone living in malaria-prone areas should use one, and those who don’t have the nets should get them from health centres.


Dr Kevin O Opondo is a malaria post-doctoral researcher at the Medical Research Council Unit in the Gambia