Polycyclic aromatic hydrocarbons and lead in roadside lettuce and rye grain



Thirty-eight samples of lettuce and three samples of rye from an experimental site close to a highway were analysed for 20 polycyclic aromatic hydrocarbons (PAH) and lead. The lettuce plants were grown 8–65 m from the road and collected after 5,9 and 11 weeks of exposure. The levels of benzo[a]pyrene (BaP) and lead varied from 0.1 to 1.3 μg kg−1 and from 0.18 to 1.6 mg kg−1, respectively. The plants grown close to the road and with long exposure times showed the highest levels. The positive gradients for PAH and lead with exposure time and closeness to the road were nearly identical, but in different concentration ranges. Lettuce plants grown in a cold frame showed lower levels than those grown in the open. In rye sampled at 7–25 m from the road, BaP was not detected and lead levels ranged from 0.07 to 0.11 mg kg−1. The results suggest that the Swedish National Food Administration/National Environmental Protection Board recommendations, i.e. not to grow leafy vegetables closer than 25 m from roads with intense traffic, are sufficient at traffic flows of up to 12 000 vehicles per day.