CFIA T-4-93 — Canadian safety standards for heavy metals in fertilizers and supplements
T-4-93 is the Canadian Food Inspection Agency’s consolidated standard document for all safety requirements governing fertilizer and supplement products regulated under the Fertilizers Act. It covers prohibitions, upper limits for contaminants (metals, dioxins/furans, indicator organisms), tolerances for micronutrient fertilizers, and acceptable analytical methods. The metals standards are based on maximum acceptable cumulative metal additions to soil over a 45-year horizon and apply to total (not extractable) metal content. All fertilizers and supplements — including processed sewage sludge, composts, and other by-products — must meet these standards.
Key numbers
Maximum acceptable cumulative metal addition to soil over 45 years (kg metal/ha), and example maximum acceptable product concentrations (mg metal/kg product) at three annual application rates:
| Metal | Max cumulative (kg/ha, 45 yr) | At 4400 kg/ha/yr | At 2000 kg/ha/yr | At 500 kg/ha/yr |
|---|---|---|---|---|
| Arsenic (As) | 15 | 75 | 166 | 666 |
| Cadmium (Cd) | 4 | 20 | 44 | 177 |
| Chromium (Cr) | 210 | 1,060 | 2,333 | 9,333 |
| Cobalt (Co) | 30 | 151 | 333 | 1,333 |
| Mercury (Hg) | 1 | 5 | 11 | 44 |
| Nickel (Ni) | 36 | 181 | 400 | 1,600 |
| Lead (Pb) | 100 | 505 | 1,111 | 4,444 |
| Selenium (Se) | 2.8 | 14 | 31 | 124 |
| Thallium (Tl)* | 1 | 5 | 11 | 44 |
| Vanadium (V)* | 130 | 656 | 1,444 | 5,777 |
| Zinc (Zn) | 370 | 1,868 | 4,111 | 16,444 |
*Thallium and Vanadium are not universally required; requested case-by-case. The Cd maximum cumulative addition of 4 kg/ha over 45 years corresponds to a maximum product concentration of 20 mg Cd/kg at a 4,400 kg/ha/yr application rate. Note that copper (Cu), molybdenum (Mo), and zinc (Zn) are essential plant nutrients and are handled under separate provisions. Standards apply to total metal content, both dry weight and as-is bases (must be consistent on the same product label).
Methods (brief)
Regulatory document, no analytical methods described for the standards themselves. The document states that acceptable methods for analysis must meet CFIA requirements; specific approved methods are referenced separately. Standards framework: cumulative soil-loading model over 45 years, accounting for metal persistence in soil, plant uptake factors, soil pH, and cation exchange capacity. Applies to hydroponics (soilless) applications using worst-case scenario modelling.
Limitations
Standards reflect maximum acceptable cumulative loading, not current product concentration limits in isolation; the applicable limit depends on the product’s annual application rate stated on the label. No speciation is required for metals (total metal basis), which means chromium limits are total Cr, not Cr-VI. The document accessed on 2026-05-12 shows URL dated 5/12/26, 5:54 PM; CFIA updates this document periodically and it should be checked for current revision date.
Implications
- Certification: Canadian T-4-93 is directly relevant for HMT&C supply-chain and fertilizer-input standards. The Cd limit of 4 kg/ha cumulative (equivalent to 20 mg/kg at 4,400 kg/ha/yr application) is among the most protective in the world for Cd in fertilizers. Brands sourcing organic produce that uses certified compost in Canada must meet these standards. The As cumulative limit of 15 kg/ha (75 mg/kg product at high application rates) is also relevant for phosphate fertilizer sourcing.
- Courses: Essential reference for supply-chain modules covering how agricultural inputs introduce heavy metals to soils and eventually to crops; the 45-year cumulative model illustrates why legacy contamination from fertilizer use persists long after application stops.
- App: Fertilizer and soil-amendment sourcing is a key upstream driver of food-crop metal contamination; this standard defines the Canadian regulatory floor for input control.
- Microbiome: Not applicable.