Pesticides and antibiotics in Nile tilapia (Egypt)

Overview

Eissa F et al.. Toxicol Rep 2020 · PMID 33384941 · DOI 10.1016/j.toxrep.2020.03.004

Most wild river tilapia sampled near drains had pesticide traces (chlorpyrifos above the EU limit in 45%) and a fifth had antibiotic traces, including EU-banned drugs; estimated non-cancer risk was low.

Does the study support the specific claim? Partly · Methodological quality: moderate

Original publication

Plain-language summary

Scientific in-depth review

1. Full reference

Authors

Eissa F et al.

Journal

Toxicol Rep

Year

2020

Identifier

PMID 33384941 DOI 10.1016/j.toxrep.2020.03.004

Verification

verified – PubMed efetch 2026-10-25

Retracted

no

Corrections

none

Extent checked

full text

Conflicts of interest and funding

Authors report no competing interests; no funding statement; acknowledgement to the Central Laboratory of Residue Analysis of Pesticides and Heavy Metals in Food, Agricultural Research Center, Egypt.

2. Research question

Pesticide/antibiotic residues in Nile tilapia from the Rosetta branch and consumer risk

3. Study design and population

Study design

Measurement / residue study – One-year monthly residue monitoring (100 pesticides, chloramphenicol and 4 nitrofuran metabolites) in wild Nile tilapia caught near agricultural/wastewater drain outlets, with deterministic non-carcinogenic risk assessment (THQ)

Population

Wild Nile tilapia (Oreochromis niloticus) caught with local fishermen 1 km upstream of the El-Rahawy (Giza), Sabal (Minoufiya) and Tala (Gharbiya) drain outlets on the Rosetta branch

Country

Egypt

Period

July 2018-June 2019

Sample size

72 fish muscle samples (3 sites x 12 months, in duplicate)

Inclusion and exclusion criteria

Not applicable; dorsal muscle (edible part) analysed

4. Methods and endpoints

Exposure / intervention

Sampling site and season

Comparator

EU MRLs; US EPA reference doses (THQ threshold 1)

Endpoints

Residue frequency and concentration; THQ assuming 38.14 g fish/day, 60 kg body weight, 70-year exposure

Statistical methods

Descriptive (frequencies, ranges, seasonal/site means); QuEChERS GC-MS/MS and LC-MS/MS; ISO/IEC 17025-accredited lab (FINAS); recoveries 62-120% (pesticides), 85-97% (antibiotics); LOQ 0.01-0.05 mg/kg (pesticides), 0.075-0.5 ug/kg (antibiotics)

5. Actual results

Results

62/72 (86%) samples contained >=1 pesticide; chlorpyrifos in 83% (<LOQ-0.08 mg/kg), exceeding the EU MRL (0.01 mg/kg) in 45% of samples; p,p'-DDE in 45% (<LOQ-0.04 mg/kg); tebufenpyrad 8%; others <=3%. 15/72 (21%) contained antibiotic residues: nitrofurazone (SEM marker) 8.6-52 ug/kg in 12% (all from Sabal in spring), nitrofurantoin (AHD) 1.1-2 ug/kg in 6%, chloramphenicol <LOQ-0.17 ug/kg in 5%; none in autumn and winter. Highest loads at Sabal. All THQ <1 (max p,p'-DDE 0.06, chlorpyrifos 0.03, nitrofurazone 0.01661).

Absolute risks

not reported (THQ screening indices only)

Authors' conclusion

Consumption of Nile tilapia from the Rosetta branch is unlikely to cause detrimental effects and can be considered safe for ordinary consumers; laws should be enforced, wastewater treated and monitoring continued; detection of banned nitrofurans and chloramphenicol indicates continued use in food-producing species.

6. Strengths

• Year-round monthly sampling at three sites
• Wide analyte panel with accredited, validated methods
• Separate site and season reporting

7. Weaknesses

• Wild river fish sampled close to drain outlets (worst-case locations), not market or farmed fish
• Small n per site-season; antibiotic findings driven by one site-season (Sabal, spring)
• THQ is inappropriate for genotoxic carcinogens (nitrofurans, chloramphenicol have no safe threshold); no carcinogenic risk or cumulative (hazard index) assessment
• Nitrofurazone inferred from SEM marker, which is not fully specific (reviewer note)
• Single fish intake scenario; children not assessed
• No funding statement

8. Risk of bias

Orienting tool

No standard tool fits (residue monitoring/exposure assessment); structured validity judgement

Type of assessment

structured assessment based on the full text by a single reviewer (no formal double review)

Full formal assessment

no

Overall risk of bias

some concerns

Rationale

Single-reviewer structured judgement based on the full text; not formal (needs two independent reviewers). Changed from low to some_concerns because of purposive near-drain sampling and the THQ approach for genotoxic residues.

Full-text review (25 October 2026): Added sampling near drain outlets, chlorpyrifos MRL exceedance in 45%, antibiotic findings concentrated in one site-season, analytical validation, THQ assumptions and values, missing funding statement; noted THQ unsuitable for genotoxic residues; bias overall changed from low to some_concerns.

9. Assessment of the statistical interpretation

THQ <1 indicates low non-cancer risk at the assumed intake; it does not address the regulatory zero tolerance for nitrofurans and chloramphenicol, whose presence is a compliance signal independent of THQ. Frequencies are based on 72 samples (6 per site-season).

10. Relevance to the specific claim

C-FSH-09, C-FSH-12, C-FSH-16, C-RES-01/02. Note: these are river (not farmed) tilapia - residues come from the environment.

11. Independent contrary findings

12. Transferability to Germany and Europe

Low (Egypt-specific).

13. Overall methodological judgement

Egyptian evidence that wild river tilapia near drains carry pesticide residues (chlorpyrifos above EU MRL in 45%) and occasional banned antibiotic residues, at levels the authors judge low-risk for non-cancer effects. It concerns wild, not farmed fish, so it does not support claims specific to farmed fish feed; it rather shows that 'natural' river fish are not automatically clean.

14. Open questions

Farmed and market tilapia with the same panel; carcinogenic risk assessment for nitrofurans; source attribution of residues.

15. Linked fact checks

• Farmed fish (e.g. tilapia, mullet) are forbidden because their food is not clean: they are fed poultry manure and poultry offal, and the waste of fish farms is in turn fed to cattle. – Studies contradicting or limiting the claim
• Current agricultural practices - feeding animals unnatural feed and using hormones - produce contaminated food (archive quote attributed to the episode 'The New Food Pyramid', January 2026). – Studies supporting the claim
• Everyday foods carry 'explicit toxins': residues of antibiotics, fertilisers, stimulants/growth promoters, chemicals and pesticide residues, which the body must deal with daily. – Studies supporting the claim
• Pesticide, antibiotic and hormone residues in food are a main cause of chronic health problems (implied by his theory statement and recurring remarks such as 'you are poisoned: the amount of pesticides and hormones'). – Studies supporting the claim