He studied between 1968 and 1974 and earned his PhD in 1979 at the Wageningen University and Research with the thesis The Relationship between Microsomal Enzyme Induction and Liver Tumour Formation".
Tennekes wrote in 2010 the book "A disaster in the making", about the dangers of neonicotinoids, a new generation of pesticides for insects and bees in particular.
[4][5] Initially, his vision had strong opposition as his findings were criticized, but follow-up research partially confirmed his warning.
Since the end of 2018, the use of three neonicotinoids (clothianidin, thiamethoxam and imidacloprid) has been banned in the European Union.
[6] Tennekes who used to work as a freelance researcher for chemical companies found himself blacklisted, and lost all his clients, but that didn't deter him, because he considered it his moral duty.