there's something in your hair ...

Hair is used by the United States Environmental Protection Agency (EPA) as the preferred means for monitoring environmental toxic metal exposure within the body. Mineralysis' laboratories in the US have analysed more than 350,000 samples and, in conjunction with EPA guidelines, have determined the following thresholds. Levels beyond these could indicate a potentially harmful degree of exposure.

Arsenic: 1.4 mg/kg (or 1.4 milligrams per kilo of hair) Berylium: 1.0 mg/kg Mercury: 2.1 mg/kg Cadmium: 0.80 mg/kg Lead: 11.0 mg/kg Aluminium: 22 mg/kg 1 Chan Chi-ko, 16, boarding-school pupil, Stanley Arsenic: below calibration limit (bcl) Berylium: bcl Mercury: 3.7 mg/kg Cadmium: 0.1 Lead: 0.1 Aluminium: 5 Chan prefers eating meat and avoids vegetables. He has seafood occasionally and eats out at restaurants about twice a week. Ballgames and playing guitar are his favourite pastimes. He plays volleyball and football at least five times a week. He enjoys school life and feels lucky to be living among so much greenery in Stanley.

2 Kenneth Cheung Ka-wai, 20, student at Hong Kong University, Pokfulam Arsenic: 0.2 mg/kg Berylium: bcl Mercury: 0.32 Cadmium: 0.6 Lead: 2 Aluminium: 6 Cheung usually eats instant noodles at the university's residence and when he eats out, usually at the university canteen, he orders meat dishes with few vegetables. He does not eat fish. Besides a weekly jog around the campus and a weekly hockey session, Cheung spends most of his free time on the Internet and playing video games. As an industrial engineering student, he oftens come into contact with chemical substances and industrial machinery as he carries out experiments.

3 Chim Lai-king, 22, police constable in Wong Tai Sin, lives in Kwun Tong Arsenic: bcl Berylium: bcl Mercury: 2.9 mg/kg Cadmium: bcl Lead: bcl Aluminium: 4 According to the beat officer who spends her working hours patrolling Wong Tai Sin, the air in the district is relatively clean, because her hayfever and allergies are not such a problem there as they are at her home in Kwun Tong - the most industrialised area in Hong Kong. During the summer, her nose drips incessantly when she is at home. Chim usually eats out and prefers vegetables and fish to meat.

4 Choi Kau, 75, retired, Ho Sheung Heung, New Territories Arsenic: bcl Berylium: bcl Mercury: 2.1 mg/kg Cadmium: 0.1 Lead: 11 Aluminium: 3 Since moving from Sheung Shui town centre to the rural Ho Sheung Heung village near the border two years ago, following a stroke, Choi has rarely been into town. The air quality, she says, is noticeably better. Eating out has never been a habit and her diet consists solely of fish and vegetables. Because she can barely walk, stretching is her only means of exercise.

5 Toby Emmet, 54, retired, Hoi Ha, Sai Kung Country Park Arsenic: bcl Berylium: bcl Mercury: 0.7 mg/kg Cadmium: 0.1 Lead: 1 Aluminium: 11 Living in a house by a river, amid beautiful grasslands and his own livestock, Emmet is a Machlehose Trail junkie: he takes part in the annual Trailwalker fund-raising event every year and goes on at least two long walks and one 10 km - 20 km bike ride every week. He believes pollution in Hong Kong is worsening and notices the air pollution on his trips to the city. China is the most significant source of pollution in Hong Kong in his opinion. He has been diagnosed with skin cancer. Emmet dines out most evenings but doesn't eat shellfish to avoid toxic poisoning.