Long term exposure to air pollution in London is linked to higher blood pressure in teenagers, a study by King's College London has found. 

Scientists from KCL analysed data from over 3,000 adolescents and found a correlation between exposure to high levels of nitrogen dioxide (NO2), a pollutant from diesel traffic, and lowering blood pressure. 

Clean Air for Southall and Hayes found on Monday 6th February that their node in Southall recorded a nitrogen dioxide level of 167.96 µg/m3 at 7pm, over four times the annual mean level for the UK, and higher than the same date and time for Hanger Lane, 141.01 µg/m3, where you would expect greater traffic. 

The researches said in the article: "This longitudinal study in London, England, indicates that air pollution appears to have a considerable impact on BP during adolescence, and in girls more than boys. 

"We hypothesised that long-term exposure to poor air quality would be associated with higher BP, but found a mixed picture, varying in direction by pollutant. Associations were significantly modified by sex. 

"Ethnic-specific associations were not evident despite cumulative, marginally higher exposures to modelled annual average NO2 and PM concentrations among Black Caribbeans, Black Africans and Pakistani/ Bangladeshis than their White UK peers. Associations did not vary by SEC or BMI. 

"A negative NO2-BP [blood pressure] relationship can be biologically plausible as we have shown that NO2 feeds into the (nitrate)-nitrite-nitric oxide (NO) pathway and acutely lowers BP." 

The study looked at people from a diverse range of places across London and they found that the greater the increase in exposure to nitrogen dioxide was associated with lower systolic blood pressure, with a starker change in women. 

The study also found that whilst there was no greater or lesser association based on ethnicity, but that ethnic minority groups were exposed to greater levels of nitrogen dioxide than the white people involved in the study. 

The scientists also said that further research was needed in this area to confirm their findings, particularly looking into children from different socio-economic backgrounds.