[Bioaccessibility of lead in urban topsoil and its health risk assessment: a case study of a small area near Shougang Group].

Bioaccessibility and health risk of lead in urban topsoil after unconscious oral ingestion were studied. 65 topsoil samples were collected from a small area near Shougang Group, and then bioaccessibility of soil lead was measured by means of in vitro digestion test. Results showed that the bioaccessibility of soil lead covered a wide range (28.83%-62.50% in gastric phase, and 6.86%-45.71% in intestinal phase), and had no relation to its total concentration. It was also found that the high-value areas of the gastrointestinal dissolved concentration of soil lead distributed in nearly the same way as those of its total concentration. Besides, high gastrointestinal dissolved concentration and low bioaccessibility of soil lead were observed in the sample sites close to traffic and vehicles. Due to low contribution rate of the bioaccessible amount of soil lead to the provisional tolerable weekly intake (PTWI), the health risk of soil lead in the studied area was generally low. Only when health risk assessment was based on the gastric data of children (the worst case), the sample with highest contribution rate, 25.37%, was found in the northwestern part of the studied area, where the other 5 samples with contribution rate over 10% were also located. It was obvious that the health risk of soil lead to children was higher than that to adults. Due attention should be paid to the soil with both high total concentration and high bioaccessibility of lead, as it might pose high risk to the health of general public.