Fipronil is a very effective agent against termites. Fipronil has a moderate acute toxicity to people and mammals. It is slightly to moderately toxic when absorbed through the skin.

The EPA has fipronil classified as a possible human carcinogen (NPIC): it should be emphasised that this a precautionary classification. The inhalation of fairly large amounts of fipronil may cause convulsions and tremor (NIOSH) and small amounts may have some adverse effect. Exposing the eyes can cause irritation (PANNA). Long term effects of continuing exposures are unknown.

Like most pesticides, it is safe if applied with care to prevent exposure of people or nontarget animals and, with this proviso, it is a safe and effective choice. However, It should only be used in the home with good ventilation and with a minimum exposure to adults and none to children, especially babies. They should not be present when spraying is carried out although I should expect the sprayed area to be safe after about an hour with good ventilation.

With regard to the office, I think that spraying or other application on a Saturday when the office is empty and left empty until Monday, even without ventilation over this period is safe provided the windows are opened for an hour or so before or when workers arrive on Monday. I doubt if there are safer effective options to combat termites. The key to personal safety with any pesticide is always to minimise human exposure and particularly inhalation, skin contact or contamination of food and drink.

A fact sheet prepared by staff at the UK Natural Resources Institute was prepared for Pesticide Action Network UK (PAN UK) and is available at: http://www.pan-uk.org/pestnews/Actives/fipronil.htm

This concludes that: "Fipronil ... can generally be applied at low to very low dose rates to achieve effective pest control. Questions have been raised about suitability [of fipronil] for use in IPM and studies suggest that this must be evaluated on a case by case basis.

In certain situations it may disrupt natural enemy populations, depending on the groups and species involved and the timing of application. Its acute toxicity varies widely even in animals within the same groups. This means that the toxicological findings from results on standard test animals are not necessarily applicable to animals in the wild.

Testing on local species seems particularly important in determining suitability of fipronil based products for registration in different countries or habitats and the likely risk to non-target wildlife. Fipronil use requires careful consideration where contamination of the aquatic environment is likely, due to its high toxicity to some fish and aquatic invertebrates. ... in developing countries where illiteracy, lack of protective clothing and use of insecticide drums increase the risk of human contact with the product at above recommended dose rates, a precautionary approach may be warranted.

In general, it would appear unwise to use fipronil-based insecticide without environmental monitoring to accompany its use, in situations, regions or countries where it has not been used before and where its use may lead to its introduction into the wider environment or bring it into contact with people."

A detailed (30-page) briefing on fipronil, prepared by ecotoxicology experts, is available from PAN UK at http://www.pan-uk.org/archive/Publications/Briefing/fipronil.pdf