Ye et al. 2026 — Tin in foods and dietary exposure, Zhejiang Province, China
This comprehensive provincial survey measured total tin (Sn) concentrations in 2014 food samples across five major categories (fresh vegetables, tea, fresh aquatic products, fresh fruits, and canned foods) in Zhejiang Province, China, and assessed dietary exposure risk across five age groups using matched consumption data from a 2015–2017 nutrition survey. Canned foods, particularly acidic canned fruits (mean 12.67 mg/kg, max 134 mg/kg), contained the highest Sn concentrations by far; fresh vegetables, fruits, and most aquatic products had uniformly low concentrations. All total hazard quotients (THQ) for inorganic Sn remained well below 1 across all scenarios, indicating minimal inorganic Sn health risk under current dietary patterns. A separate organotin analysis using a conservative reverse dietary risk approach found that only 0.16% of total Sn in canned foods or 0.37% in fresh aquatic products would need to be organotin species to reach the organotin TDI, highlighting that while total Sn is safe, organotin speciation in these high-risk categories warrants ongoing monitoring, particularly for children aged 6 years and under.
Key numbers
All Sn concentrations expressed on dry weight (dw) basis unless noted otherwise.
Fresh vegetables (mg/kg dw; n=673):
| Subcategory | Mean | P50 | P95 | Max |
|---|---|---|---|---|
| Solanaceous | 0.04 | 0.00 | 0.27 | 0.34 |
| Cruciferous | 0.01 | 0.00 | 0.03 | 0.04 |
| Cucurbit | 0.01 | 0.00 | 0.04 | 0.04 |
| Tuber and root | 0.06 | 0.00 | 0.33 | 4.53 |
| Aquatic vegetables | 0.01 | 0.01 | 0.04 | 0.10 |
| Leafy vegetables | 0.04 | 0.00 | 0.21 | 1.14 |
Tuber and root vegetables show the highest Sn among fresh vegetables (mean 0.06 mg/kg, max 4.53 mg/kg), attributed to soil contact and surface adsorption.
Tea (mg/kg dw; n=378): Green tea: mean 0.08, P50 0.03, P95 0.37, max 1.30 Black tea: mean 0.08, P50 0.04, P95 0.31, max 0.57 Oolong tea: mean 0.13, P50 0.03, P95 0.31, max 2.02 Dark tea: mean 0.08, P50 0.03, P95 0.49, max 0.57 Detection rates 76–96% across tea types.
Fresh aquatic products (mg/kg dw; n=392): Fish: mean 0.26, P50 0.01, P95 0.50, max 10.30 (detection rate 15%) Crustaceans: mean 0.02, P50 0.01, P95 0.10, max 0.40 Mollusks: mean 0.01, P50 0.00, P95 0.03, max 0.50
Canned foods (mg/kg dw; n=438): Cereal-based canned foods: mean 0.04, P50 0.01, P95 0.21, max 0.37 Canned vegetables and vegetable products: mean 1.05, P50 0.12, P95 5.13, max 19.80 Canned fruits and fruit products: mean 12.67, P50 0.15, P95 80.73, max 134.00 Canned meat and meat products: mean 0.96, P50 0.03, P95 3.42, max 23.70 Canned aquatic products: mean 0.12, P50 0.02, P95 0.62, max 1.51 Canned edible fungi: mean 1.61, P50 0.06, P95 0.48, max 38.90
No samples exceeded national Sn maximum limits (canned foods: 100 mg/kg; other foods: 200 mg/kg per Chinese standards).
Health risk (inorganic Sn): All THQ values below 1 across all five age groups under all four exposure scenarios (A: P50×P50 through D: P95×P95). Maximum THQ was under scenario D for children ≤6 years: not explicitly tabulated for individual categories but ΣEDI across all foods was 65.29 µg/kg BW/day, THQ = 0.218, using RfD of 300 µg/kg BW/day (ATSDR MRL for chronic inorganic Sn exposure).
Organotin risk (reverse assessment): Minimum proportion of total Sn that would need to be organotin to reach organotin TDI (0.25 µg/kg bw/day; EFSA; or RfD 0.3 µg/kg bw/day; U.S. EPA for tributyltin oxide):
- Canned foods: 0.16% (95% CI: 0.15–0.18%)
- Fresh aquatic products: 0.37% (95% CI: 0.29–0.45%)
- Fresh vegetables: 1.15% (95% CI: 0.96–1.57%)
- Fresh fruits: 7.77% (95% CI: 7.45–8.75%)
- Tea: 18.67% (95% CI: 18.14–21.93%)
Organotin exposure from fresh aquatic products (conservative scenario, Monte Carlo): Children ≤6 years exceed the organotin TDI at the 69.3th percentile (95% CI: 68.4–70.2%), indicating that approximately 30% of children aged ≤6 years with typical consumption remain below TDI. Under Scenario C (P50 consumption × P95 contamination), THQ for organotins from aquatic products is 7.0–16.0 for all age groups.
Methods (brief)
2014 food samples from Zhejiang Province collected 2018–2019, multistage stratified random sampling. Sn by ICP-MS per Chinese national standard protocol. Samples dried before analysis; concentrations reported on dry weight basis. LOD: 0.004 mg/kg (vegetables, fruits, aquatic products, canned foods); 0.008 mg/kg (tea). Non-detects substituted at half the LOD per WHO guidelines. Consumption data from 2015–2017 Zhejiang Nutrition and Health Surveillance (approximately 10,000 participants; 3-day, 24-hour dietary recall). Age groups: ≤6, 7–12, 13–17, 18–59, ≥60 years. Body weight 57 kg (provincial survey mean).
Critical species note: All Sn concentrations are total Sn. The paper explicitly distinguishes inorganic Sn from organotin compounds, noting that organotin compounds are substantially more toxic (EFSA TDI for sum of TBT+DBT+TPT: 0.25 µg/kg bw/day vs. inorganic Sn MRL: 300 µg/kg bw/day — a ~1200-fold difference in toxicological threshold). Organotin speciation (TBT, DBT, TPT, DOT) was not directly measured; the organotin risk assessment used a conservative reverse approach with a literature-derived proportion of 5.83% organotin-to-total-Sn from mollusks as a benchmark. This is a conservative upper-bound assumption for most food categories.
Implications
Certification: This study provides the most comprehensive regional food-category Sn dataset available for China as of 2026. Canned fruits are the highest-Sn food matrix by a wide margin (mean 12.67 mg/kg, max 134 mg/kg); all remain below regulatory maxima but represent an important fraction of dietary Sn load. HMT&C Sn analyte coverage applies primarily to canned products; fresh vegetables and fruits present negligible Sn exposure. The organotin analysis, while based on a conservative model rather than direct speciation, is important: it establishes that the margin between total Sn and the organotin toxicological threshold is narrow for canned foods and fresh aquatic products, meaning direct organotin measurement in those matrices is warranted for future certification or monitoring programs.
Courses: Illustrates the inorganic-Sn vs. organotin distinction operationally: total Sn measurements that look safe under inorganic Sn thresholds may carry hidden organotin risk, and the speciation gap in food monitoring is identified as a data limitation. Fresh vegetables present minimal Sn risk compared to canned products.
App: For Sn risk scoring: canned fruits carry by far the highest Sn exposure load; canned vegetables and canned fungi are intermediate; fresh vegetables, fresh fruits, and fresh aquatic products are low. The maximum fresh-vegetable Sn value (tuber/root: 4.53 mg/kg dw) is a realistic upper bound for non-industrial produce but is orders of magnitude below canned-product maxima.