Sushi consumption rates and mercury levels in sushi: ethnic and demographic differences in exposure

There are few papers on sushi consumption and its role in methylmercury exposure. We interviewed 1289 people in a New Jersey university community regarding fish and sushi consumption and collected 'sushi' samples for total mercury analysis from New Jersey stores and supermarkets and from New York City, and Chicago. The 92% of interviewees who ate fish, ate an average of 5.06 fish and fish-sushi meals/month; 77% of interviewees reported eating sushi (mean = 3.27 meals/month). Caucasians and Asians ate more sushi meals/month, and more sushi pieces/meal than other ethnicities, with East Asians eating more than South Asians. Some people in all ethnic groups ate more than 40 fish-sushi pieces/ month. Total mercury levels varied significantly by type and quality of sushi, with tuna sashimi having the highest mean levels (0.68 ± 0.05 μg/g = ppm on wet weight basis equivalent to about 0.61 ppm of methylmercury). Tuna roll averaged 0.46 ± 0.09 ppm of total mercury. Other types of sushi averaged less than 0.06 ppm total mercury. Eight interviewees reported eating fish or fish-sushi meals at least daily. We estimated mercury exposure at the 90th percentile of fish-sushi consumption, assuming an average 19.3 g of fish per piece of sashimi grade tuna (averaging 0.608 ppm MeHg), using the USEPA recommended default body mass of 70 kg and the Reference Dose of 0.1 μg/kg/day. The methylmercury intake was estimated at 0.34 μg/kg/day which exceeds the EPA Reference Dose. The top 10% of all ethnic groups exceeded the Reference Dose while Caucasians and Asians exceeded the CDC/ATSDR's Minimal Risk Level of 0.3 μg/kg/d, as well as the WHO Provisional Tolerable Weekly Intake (1.6 μg/kg). The large tuna such as Bluefin, which are prized for sushi, have the highest mercury levels and are also the most endangered by overfishing. These data suggest that sushi can pose a significant risk from mercury exposure.