Impact of cooking and processing on arsenic concentrations and dietary risk in rice products from central Taiwan

Inorganic arsenic (iAs) is a known human carcinogen and a major dietary concern in rice-consuming populations. To address limited data on arsenic exposure from rice products, this study surveyed 45 table-ready rice items collected in Taichung (population ≈ 2.9 million) and estimated dietary exposure using Monte Carlo simulation. Total arsenic (tAs) and iAs concentrations were analyzed to assess the impact of cooking and processing methods. Steamed plain rice, particularly glutinous and brown varieties, had the highest iAs (34.2–69.8 μg/kg) and moderate tAs (57.9–149.9 μg/kg), whereas composite products (e.g., onigiri, zongzi) showed lower iAs (19.0–37.3 μg/kg) but higher tAs (70.1–299.5 μg/kg), reflecting non-rice ingredient contributions. Powdered and beverage items (e.g., multigrain powder, rice milk), as well as rice noodles and cakes (e.g., rice sticks, Mitaimu), showed the lowest iAs (5.0–20.9 μg/kg) and tAs (12.5–36.8 μg/kg), likely due to arsenic dilution or leaching during processing. Estimated mean iAs intake was 0.23 μg/kg bw/day for adults, with toddlers showing nearly double the exposure. Compared with Western populations, Taiwanese intakes were higher due to greater rice consumption, with plain and glutinous rice as dominant contributors. Although all iAs concentrations were below regulatory limits, ongoing monitoring is recommended, especially for toddlers. • Ready-to-eat rice products in Taiwan analyzed for total and inorganic arsenic. • Cooking and processing strongly influenced arsenic levels and speciation. • Steamed plain rice had the highest inorganic arsenic among all rice types. • Monte Carlo simulation estimated dietary arsenic exposure for adults and toddlers. • All samples met regulatory limits; toddlers showed higher exposure than adults.