For anyone looking at this post to see if they can apply
Pyrethrum (rather than synthetic permethrin)
to clothing (not as a agricultural insecticide), does anyone know the safe amount of concentration of Pyrethrum solution for this to be safe? Any books or research to dig through to learn the risks?
I've tried searching around and can't find much so far, just super thankful for the reply Cris Bessette had earlier linking to
http://www.livingwithbugs.com/permethrin_pyrethrum.html . My research so far is showing that most concentrates are only listed as agricultural insecticide. Permethrin-based products for clothing seem to have around a permethrin portion of 0.5-0.52%.
Considering growing chrysanthemums too, sounds like there's different risks though (some grow like weeds and might be allergic to them). Hearing from parents some of the sold pyrethrum might be extracting from Feverfew (Tanacetum parthenium / Chrysanthemum parthenium / Pyrethrum parthenium).
John Casida - Pyrethrum The Natural Insecticide (1973) touches on earlier experiments on human using 0.2% concentration: (see page 236 or attachment) -
https://www.google.com/books/edition/Pyrethrum/vz2-kF6NKeIC?hl=en&gbpv=1
You have to be fairly careful with pyrethrins, Cox, 2002, JOURNAL OF PESTICIDE REFORM (
https://d3n8a8pro7vhmx.cloudfront.net/ncap/pages/26/attachments/original/1428423441/pyrethrinspyrethrum.pdf?1428423441 via
https://www.pesticide.org/pesticide_factsheets ) states:
"Pyrethrins disrupt the normal functioning of sex hormones. They inhibit binding of sex hormones to human genital skin and proteins in human blood.
Pyrethrins are classified as “likely to be human carcinogens” by EPA because they cause thyroid tumors in laboratory tests. Farmers who use pyrethrins have an increased risk of developing leukemia."
Cox also states risks around permethrin - notably in household treatments:
https://d3n8a8pro7vhmx.cloudfront.net/ncap/pages/26/attachments/original/1428423343/cypermethrin.pdf?1428423343