Biomonitoring seasonal changes in the environmental impact of atmospheric pollution around junction 16 of the M25 London Orbital Motorway (a high traffic area), United Kingdom.

Larvae of a lichenophagous bagworm moth, Luffia ferchaultella [Stephens 1850], were used to monitor the potential environmental impact of pollutants from a diffuse emission source, exhaust emission products, around Junction 16 of the M25 London Orbital motorway where it interchanges with the M40 motorway. Larvae were fed terrestrial epiphytic algae, collected on four occasions over a 3.5-year period, from 17 sites located within a 16 km(2) survey area. After 10 days of exposure to algae from certain sites, large reductions in the amount of fecal material (frass) produced by the larvae were noted. These reductions correlated with the concentrations of exhaust-related metals in the algae. On all four sampling occasions one site, located close to the junction, had some of the highest levels of exhaust related contaminants and resulted in significantly reduced larval frass production. Geostatistics were used to map the extent of the affected areas. On all four sampling occasions sites located down wind, to the east of the interchange, were statistically significantly affected. This area of impact increased in extent from 1998 to 2000, when a second area of contamination developed to the south west of the junction. By January 2001 the extent of the impacted area in the south west of Junction 16 had increased, while that to the east had declined. By September 2001 the extent of the impacted area to the west of the junction had spread still further, while the impacted area to the east remained reduced when compared with the situation found in 1998.