Background pollution occurs in areas not directly affected by pollution sources.

The site is sufficiently isolated that it can be used to measure the background pollution levels in the high Arctic troposphere.

The department blamed the figures on unfavourable weather conditions, worsening background pollution and the number of ageing vehicles on streets.

B0070 Background pollution The pollution that would exist at a given point if it were unaffected by pollution arising from a specific source.

Chronic Effects DR Comparing exposure from the kiln with tobacco smoke - background pollution.

The researchers found that emissions of ultrafine particles, which are less than 1/500th width of a human hair, were significantly elevated when compared to background pollution levels.

Justification The value of 7 µg/m3, below which no reduction is necessary, reflects hemispheric background pollution, which is uniform across Europe.

The marsh at the bottom of the lands has been used in film documentaries, as it is the only place in Cumbria where there is not "background pollution".

The first, such as poor climate, dry conditions, the genetic make-up of the tree, the nutrient status of the soil, background pollution and the degree of competition from neighbours, will predispose a tree to succumb to stress.

Justification A straightforward and fair way of taking account of Member States’ differing starting points and, hence, differing potential for reduction is firstly to subtract hemispheric background pollution and then to calculate the 20% reduction target in a more ambitious fashion.

Within- and among-tree variation in assemblages of endophytic fungi in Scots pine (Pinus sylvestris) needles were studied in a subarctic area where background pollution values are low; the effects of tree density and prolonged simulated acid rain on the occurrence of endophytic fungi were investigated.

"Because of relatively high levels of background pollution in our study area and possible misclassification of exposure, we cannot completely rule out an adverse effect, and further study is needed that incorporates life-time exposure to pollution in populations with wide variation in exposure," they write in the journal BMC Pulmonary Medicine.