Fright factor', a neat phrase for irrational fears we have of the (usually technological) unknowns we meet. For instance we are almost hysterically opposed to mobile phone masts whilst we are quite happy to clamp mobile microwave ovens to our heads!

This misperception of risk can have unfortunate consequences. Take the case of the bitterly opposed municipal waste incinerators. Nobody wants them yet they are one of the few sustainable technologies we have in the field of waste disposal.

You report that David Evennett says we want clean, not polluting technologies and lumps the proposed Thames Gateway bridge and the Belvedere incinerator into some kind of ugh, dirty' common categorisation.

Incinerators emit negligible pollutants you can scrutinise the records for yourself (www.onyxgroup.co.uk/pdfs/selchpairreport.pdf). They emit only carbon dioxide which is a greenhouse gas (but derived from a renewable source i.e. the waste) and inert bottom ash.

The SELCHP incinerator in Deptford takes some of Bexley's waste but cannot take it all.

The unsustainable alternative is landfilling, and we are rapidly running out of sites, hence landfill tax which is now £35 per tonne, about twice the price of incineration.

It is ironic that the success of the local pressure group BADAIR in delaying the Belvedere incinerator means that Bexley's council tax will have to rise considerably, now and for years ahead to pay for landfilling its waste which would otherwise have gone there.

You can blame the man who said it was "landfill in the sky" for that one!

Another sad matter is speed humps, the response to which is for people to buy SUVs because they ride over them, much bigger vehicles, much more polluting. Our children live at exhaust-pipe level, they won't get asthma from a 100m high incinerator chimney!

Toby Clark, Grazeley Close, Bexleyheath