Hazard identification and risk assessment of pyrethroids in the indoor environment

Household insecticide products raise several important considerations conce rning safety. These are related to the use of insecticides by untrained ind ividuals, the difficulty of controlling the use of these products once purc hased by the consumer and the potential exposure of the very young and very old, possibly with or without pre-existing pulmonary disease. Exposure to pyrethroids contained in mats or vaporizers, being slow release systems, ha ve particular potential for long-term low-level exposure whilst for foggers , spray-cans or sprayed formulations the short-term high-level exposures ma y be of more concern. According to the volatility of the active ingredient contained in the household insecticide, its persistence in a non-inhalable matrix, i.e. sedimented house dust, may be short or long for highly volatil e or low volatile active ingredients, respectively. On the other hand, the potential of exposure is apparently just reciprocal. This demonstrates that the extent and duration of exposure may be highly product-specific. Accord ingly, the extent of exposure has to be accounted for and for risk assessme nt both concentration-dependent (e.g. sensory irritation) as well as concen tration x time (= dose) related effects have to be considered and addressed in adequate bioassays. The issue as to whether pyrethroids adhering to hou se dust is of concern has been addressed in a model study using carpets tre ated with pyrethroids. This study has demonstrated that the total mass of p yrethroid applied to the carpet and that brushed off within an 18-h period is too small to be of any relevance for risk assessment. Therefore, assessm ent of health hazards in the indoor environment based simply on methodologi es of emptying the household vacuum cleaner and analysing its content, whic h addresses contamination only, rather than examination of the actual airbo rne concentration, including other relevant airborne materials, is prone to tremendous errors and misjudgments. Due to the many substances potentially present in house dust and indoor air, e.g. bioaerosols originating from an imals, pests and microorganisms, volatile organic substances (VOCs) or meta ls, prudent expert judgment is needed to assess the relevance of analytical findings. The complex indoor exposure scenario makes it especially difficu lt to causally relate clinical and epidemiological findings to arbitrarily selected indicator substances contained in a matrix not readily available t o inhalation exposure. (C) 1999 Elsevier Science Ireland Ltd. All rights re served.