The lead in vegetables tested in a Baptist University study exceeded global standards by up to 2.8 times.
But the levels were acceptable under Hong Kong standards which are 20 times less stringent than those of the World Health Organisation, the European Union and Australia.
The results prompted calls for the government to review its standards for heavy metals in food.
The university took 93 vegetable samples from supermarkets, wet markets and farms between September and December last year.
The worst affected was choi sum imported from the mainland and bought in a wet market in Yuen Long. It contained 0.8596 milligrams of lead per kilogram of vegetable - 2.8 times higher than the international standards of 0.3mg/kg.
The lead in a sample of kai lan grown locally and bought in a Kowloon Tong supermarket exceeded international standards by 2.3 times. The Hong Kong standard for lead in all food products is 6mg/kg.
Professor Jonathan Wong Woon-chung, director of the university's Hong Kong Organic Resource Centre, said the government should consider adopting a stricter measure for heavy metal content in vegetables.
'The standard of 6mg/kg is for all food products, but vegetables are more likely to absorb heavy metal than some other foodstuffs,' he said.
The university also tested the samples for cadmium. Only one mainland-imported sample exceeded the Hong Kong standard of 0.1mg/kg - by 2.4 times.
Wong said the average heavy metal content in vegetables was acceptable and it would pose little health risk. An adult would need to eat at least 3.7kg of contaminated vegetables a day to have long-term health effects, he said.
Wong said dipping vegetables in water for 30 minutes could wash away 40 per cent of heavy metal.
He said leaf vegetables such as spinach and choi sum were more likely to absorb toxins. People should therefore alternate between eating these and fruit vegetables, such as eggplants and tomatoes.Topics: Health Product Issues Vegetarian Cuisine