According a report published by the U.S. Centre for Public Integrity, in the ten years to 2007, there was a 300 percent increase in reported human health problems related to the use of pyrethrin and pyrethroid pesticides.  This finding is based on an analysis of adverse reaction reports filed with the EPA by pesticide manufacturers and appears to be associated with the growing popularity of these chemicals.

Pyrethrins (chemicals extracted from the pyrethrum daisy) and pyrethroids (synthetic relatives of pyrethrins) have generally been considered to be safer alternatives to other pesticides available in the marketplace. However, in 2007, they accounted for 26% of all fatal, “major” and “moderate” adverse health incidents. While the number of fatalities was low, the number of moderate and serious incidents attributed to these chemicals was significantly greater than for any other class of insecticide.

According to the report, people with ragweed allergies and asthma may be particularly sensitive to these compounds. Some people may experience anaphylactic reactions and there are concerns about their effects on the nervous system, especially in infants and children.

With the safety of pyrethrins and pyrethroids therefore being questioned, the Centre for Public Integrity report states that the EPA has promised to review it’s database on pesticide incidents. In doing so, it will consider options including stronger warning labels, tighter regulation and more thorough testing for these compounds in the future.

Reference    

Pell, M. and Morris, J.   2008   “safe” Pesticides Now First in Poisonings   Online, Available at : http://www.publicintegrity.org/investigations/pesticides/pages/introduction/