Individual and Combined Contamination of the Heavy Metals

Overview

This source page is a mechanical bulk-ingest record for a PDF in the methylmercury infant-formula research pull. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.

Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

License:   This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License
China, we collected a total of 93 imported cat and dog food from the Chinese market produced in 2021–2022, comprising
45 cat food and 48 dog food, and determined the concentrations of lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg)
while Cr, As, Hg, and Cd had contamination rates of 100%, 100%, 85.71%, and 34.18% respectively. Dry food in cat and dog
foods, with Cr, Hg, and As having the highest contamination rates at 100%. Some samples exceed the limits set by
Hygienical Standard for Pet Feed of China (Announcement No. 20 of 2018) regarding Pb and Cr, while other heavy metals
increase over the past fifteen years(1). The pet food industry offers a wide range of food products for dogs and cats,
especially wet and dry food(2). Dry food is mainly in granular form and is the mainstay of the commercial pet food industry.
Wet pet food are usually packed in tins or pouches(3). The health and well-being of pets is a major concern for pet owners,
issues such as mold toxins and heavy metals. EU RASFF reported 34 cases of chemical hazards in pet food, of which 21
cases of heavy metal hazards(4). Research on the prevalence in food and its impact of heavy metals on pets remain limited.
accumulation, and multiplication in the food chain(5). Lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg) and arsenic
(As) are known as the most problematic heavy metals and as toxic heavy metals(6–7). Heavy metals are one of the most
notified hazards in the Rapid Alert System for Food and Feed (RASFF)(8). Cereals, legumes and tuberous roots and tubers
soil are associated with mining activities(9) and the application of livestock manure chemical fertilizers(10), which result in
prevalence of heavy metals, which contributes greatly to the accumulation of heavy metal in seafood(11).
Heavy metals are ubiquitous bio-accumulative toxicant in the environment and food chain(12), and they exert toxic effects at
very low concentrations(13), posing a priority threat to public health. Exposure to Pb can induce severe toxic effects,
impacting almost every organ system(14). Pb poisoning in dogs can have negative effects on the gastrointestinal tract,
nervous system, kidneys, cardiovascular system, and blood(15). Cd is a pervasive environmental pollutant known for its
cumulative toxicity, predominantly accumulating in the liver and kidneys(16). Cd can induce cancer in animals through
various mechanisms, and exposure to it can cause nephrotoxicity and damage to the small intestine(17). High levels of As
exposure can cause kidney disease(18). Exposure of dogs to As can lead to ulcerative dermatitis(19). Cr typically exists in
Cr(VI) is highly toxic and can cause a range of diseases(20). Lethargy, dilated pupils, tearing, and diarrhea are signs of acute
Cr poisoning(5). Santana et al(21) found that exposure of mice to Pb, Cd, and As results in varying degrees of lesions in the
renal tubules. Both organic and inorganic Hg are readily accumulated in animals(22), while the organic for, which are mainly
In 2018, China released Hygienical Standard for Pet Feed (Announcement No. 20 of 2018)(24), specifying limits for Pb, Cd,
Cr, Hg and As in pet feed (supplementary table 1). Directive EC/1881/2006(25) and its subsequent amending document set
combined occurrence of Pb, Cd, Cr, Hg, and As in imported dog and cat food collected from the Chinese market in 2021–
2022, and conducted a health risk assessment.
locations in China’s supermarket and store chains. A total of 93 pet food products were sampled, including 32 from the
United States, 29 from Spain, 17 from Thailand, 10 from Germany and 5 from New Zealand, with 45 types of cat food and 48
RH 40–60% and temperature 20–23℃. The samples were then subjected to determination and all samples were measured
FW100) to ensure that 95% of the ground samples passed a 20 mesh sieve. Canned samples were homogenised using a
homogeniser (Precision Labs, HM-7300).
According to the national standard of China, samples for the determination of Pb (GB/T 13080 − 2018), Cd (GB/T 13082 −
2021), Cr (GB/T 13088 − 2006) and As (GB/T 13079 − 2006) were digested by the dry ashing method. A 5 g sample (0.0001
g) was charred in a porcelain crucible on a DK-98-II adjustable electric furnace, followed by ashing in a muffle furnace
(Nabertherm, L9/11/B170). For Pb and Cd dettermination, 5 mL 6 mol/L HCl (Sinopharm Chemical Reagent Co.Ltd) and 5
mL 6 mol/L HNO3 (Sinopharm Chemical Reagent Co.Ltd) were added to the ashed samples. For Cr, 5 mL 20% HNO3
(Sinopharm Chemical Reagent Co.Ltd) was added to the ashed samples. Then the resulting solution was diluted to 50 mL
Samples for As determination were digested with 5 mL 150 g/L Mg(NO3)2 (Sinopharm Chemical Reagent Co., Ltd), followed

Methods (brief)

China, we collected a total of 93 imported cat and dog food from the Chinese market produced in 2021–2022, comprising
and arsenic (As) in them. Cr and As were detected in all samples, followed by contamination rate of Hg. In cat food, Cr and
foods, with Cr, Hg, and As having the highest contamination rates at 100%. Some samples exceed the limits set by
combined occurrence of Pb, Cd, Cr, Hg, and As in imported dog and cat food collected from the Chinese market in 2021–
Sample Collection and Preparation
The samples examined in this paper were pet food imports produced between 2021 and 2022 and sourced from different
locations in China’s supermarket and store chains. A total of 93 pet food products were sampled, including 32 from the
types of dog food. In terms of food form, the samples consisted of 79 dry pet food formulations and 14 canned pet food
formulations. After collection, the samples were stored according to the product storage instructions, that is the room with
RH 40–60% and temperature 20–23℃. The samples were then subjected to determination and all samples were measured
before their expiry date. Before analysis, dry food samples were ground using a grinding mill (TAISITE INSTRUMENT,
FW100) to ensure that 95% of the ground samples passed a 20 mesh sieve. Canned samples were homogenised using a
Sample preparation for heavy metal determination
According to the national standard of China, samples for the determination of Pb (GB/T 13080 − 2018), Cd (GB/T 13082 −
2021), Cr (GB/T 13088 − 2006) and As (GB/T 13079 − 2006) were digested by the dry ashing method. A 5 g sample (0.0001
mL 6 mol/L HNO3 (Sinopharm Chemical Reagent Co.Ltd) were added to the ashed samples. For Cr, 5 mL 20% HNO3
(Sinopharm Chemical Reagent Co.Ltd) was added to the ashed samples. Then the resulting solution was diluted to 50 mL
Samples for As determination were digested with 5 mL 150 g/L Mg(NO3)2 (Sinopharm Chemical Reagent Co., Ltd), followed

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

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Verification notes

Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
3171d06	2026-08-02	major	1 section added
bc84bfc	2026-08-02	major	6 sections added; narrative text revised