RFI: Source for white mosquito netting (16)
Torben, Lala: Please, don't go off the deep end. These are serious
claims and counter claims.
Lala, I agree that Torben sometimes makes exaggerated claims for his
product. He's a salesman, not a technician. In my country, there are
rules about the claims one can make in trying to sell one's product,
and I don't think Torben would yet be allowed to say that the "treat-
ment lasts as long as the net". On the other hand, one can also end
up in court if one unjustly accuses a person or company of selling a
As Torben says, WHOPES approval of the Permanet is expected. There
is, accordng to our collegaues in Geneva, a solid but still incom-
plete body of data saying that the Permanet is more wash resistant
than an ordinary net. On the other hand, WHOPES approval is NOT YET
given, and some tests with the Permanet in both London and Tanzania
have been disappointing. The best policy for now, therefore, is to
await further confirmation (or refutation) of Torben's claims aboiut
wash-resistance, and to try to avoid jumping to conclusions either
way. And of course we must remember that a degree of additional wash-
resistance (which is what the WHOPES tests will show) is NOT the same
as "lasting as long as the net" (which is what Torben claims).
Torben also said that a child would have to eat 50 nets to get a
toxic dose - another exaggeration. But that doesn't mean his product
Lala quotes, from Sullivan et al, the suggested oral NOEL (No Ob-
served Effect Level) of 1 mg/kg/day. She notes that a Permanet has
about 800mg of deltamethrin on it, and says that "this exceeds even
the highest margin of safety", and that "Permanet gives unacceptable
risks to all users, especially to babies".
Since Lala is relying on Sullivan et al, it is worth just quoting a
little of their calculations for an ordinary deltamethrin-treated net
containing 400 mg of insecticide. They estimate that as a worst case,
a newborn child could suck or chew 50 square cm of netting per night,
and would absorb the same amount of deltamethrin as would be removed
by washing i.e. 30%. This is 0.0375 mg per day. They made similar
"worst case scenario" calculations for regular dermal and airborne
exposure, adjusting their assumptions for adults, small children and
newborns. They then added up exposure from the three sources and com-
pared it to the NOEL. The margin of safety was 70-fold for a newborn,
and much larger for older people. Other calculations were made for
one-off acute exposures.
So for Torben's nets, with twice as much insecticide as an ordinary
net, the margin of safety for chronic exposure would still be 35-fold
for a newborn baby (who would suck nets), 125-fold for a young child, and
1600-fold for an adult. This seems acceptable to me.
So it is false to claim that a kid could safely eat the insecticide
from 50 nets. On the other hand it is also false to suggest that the
Permanet is dangerous. What matters is that even the most heavily ex-
posed kids, who suck nets all the time, will receive a dose that is a
good margin of safety below the NOEL.
PS: Forgive me if I'm wrong, but it seems quite a coincidence that a
message about nets should come from someone whose name, in kiswahili,
is remarkably close to "Sleep-well". I suspect that "Lala Msuri" is a
nom-de-plume, and I wonder who it belongs to. Someone in the research
game? The aid game? Another net-seller? An insecticide firm?
London School of Hygiene & Tropical Medicine
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