The problem may be in the interaction between several compounds, although in subtoxic levels for each one, some of them used by beekeeper.
It´s known that fluvalinate and cumafos lead the drones to oligospermia.
And the major problem is that the residues are acumulating in wax, raising every year it´s levels, as the processing of wax doesn´t remove them.
For instance, bromopropilate has been discharged in Germany at about nine years ago but its residues, today, are still found in wax...
The safety data sheet of Apistan (fluvalinate) says :
" 9.12 Solubility in water: insoluble at 20°C "
But its soluble in fats, so its in wax . When these levels are high, passes to polen and even to honey, where it may be found (see S. Bogdavov, V. Kilchenmann, A. Imdorf; Acaricide Residues in Beewax and Honey, 1997, Apiacta 3)
Sorry it´s in pdf and I can´t send the link but here is a summary :
Summary
We studied the contamination level of the acaricides Folbex VA (bromopropylate, BP), Perizin (coumaphos, CM) Apistan (fluvalinate, FV) and Bayvarol (flumethrine, FM) in brood combs, sugar feed, honey and in new beeswax. All samples were analysed by gas chromatography with ECD detection.
After one normal acaricide treatment, in autumn, the brood comb wax was contaminated by all these acaraicides with residues ranging from 0.03 to 48 mg/kg. The degree of contamination decreases in the following order: BP > FV ≈ CM >> FM.
The amount of these residues increases with the increase in the number or the duration of the treatments. The residues in the sugar feed were much smaller than in the corresponding brood comb wax and varied from 0.004 to 0.04 mg/kg. The residues in honey were all beyond the tolerance levels and varied from 0.003 to 0.015 mg/kg. The degree of contamination decreases in the following order: BP ≈ CM > FV. In a model study, we examined the behaviour of acaricide-contaminated old comb wax when melted into new beeswax.
The acaricide concentration in the new recycled was wax on average 1.7 times higher than in the old combs, regardless of the processing conditions (longer boiling times and higher temperatures). In 1995, the commercial samples in Switzerland contained 1 mg/kg CM, 2.5 mg/kg FV, 3.8 mg/kg BP and ≤ 0.25 mg/kg FM.
Keywords: residue, acaricide, beeswax, comb, feed, honey, fluvalinate, bromproplylate, coumaphos, flumethrine.
There are strange contradictions in the indications of laboratorys. For instance, Apivar (amitraz) in Europe, has no restricted entry interval for suppers in honey gathering (as for Canada, I think) but seven days (or ten, I´m not sure but I read something about that) in US.