On Wednesday 15th May 2013, the monitoring site on Horn Lane, Acton became the first location in London to breach the National Air Quality Strategy (NAQS) Objective for PM10 for the year. The NAQS objective allows a daily mean PM10 concentration of 50 ug m-3 on not more than 35 days per year. Provisional measurements indicate that PM10 on Horn Lane has been above this threshold for 36 days during 2013.

The Horn Lane monitoring site is located close to a regulated waste management site and other industries that add to the PM10 concentrations in the area. Horn Lane itself is a residential street with many houses and flats located close to the road.

Previous studies conducted around Horn Lane have demonstrated that particles from local industry affect the surrounding area. It is also possible that local street works have added to the PM10 burden in the area. Evidence from work around other waste management sites in London, and research undertaken in the US, suggest that elevated PM10 concentrations may extend up to 1 km along haulage routes from these types of facilities, although concentrations at 1 km will be very much less than those close to the monitoring site. The pollution measured at the Horn Lane monitoring site does not reflect pollution over Ealing or London as a whole, but it is very important with respect to exposure of local residents. Over recent years, PM10 concentrations have improved at the Horn Lane monitoring site; the 50 ug m-3 threshold was exceeded on 205 days in 2005 and this decreased to 53 days in 2012.

Note: Although the UK NAQS objective for PM10 reflects the EU Limit Value there are differences in the way that they are assessed. Assessment of whether a city or region breaches the EU Limit Value is made in the UK by DEFRA using air pollution measurements in combination with modelling. Other factors including particles from natural sources, such as sea salt particles, are also included in the EU Limit Value assessment.

Item date 16/05/2013