Bioaccumulation and potential sources of heavy metal contamination in fish species in River Ganga basin: Possible human health risks evaluation

Maurya and colleagues examined five metals in river water and seven freshwater fish species obtained from fishermen and markets around four cities in Uttar Pradesh, India, during 2016–2017. The paper separates muscle, gill and liver measurements, but its wet-versus-dry concentration basis and derived health-risk calculations are internally inconsistent. Its reported values require those qualifications.

Key numbers

River-water values are source-reported means ± SD in mg/L (Table 3):

Site	Copper	Zinc	Lead	Cadmium	Chromium
Kanpur	1.35 ± 0.25	4.74 ± 0.14	0.54 ± 0.05	0.54 ± 0.07	0.32 ± 0.06
Allahabad	2.54 ± 0.65	5.25 ± 1.25	0.62 ± 0.05	0.68 ± 0.47	0.85 ± 0.08
Mirzapur	2.54 ± 0.68	6.25 ± 3.54	0.85 ± 0.08	0.78 ± 0.12	0.36 ± 0.07
Varanasi	4.58 ± 1.54	8.44 ± 2.35	0.24 ± 0.04	0.85 ± 0.24	0.45 ± 0.06

Fish muscle means ± SD below retain Table 4’s label, µg/g wet weight, which conflicts with the dry-tissue methods description. No basis conversion is assumed. Fish results are grouped by species; the paper supplies no city-specific or seasonal fish table.

Species	Copper	Zinc	Lead	Cadmium	Chromium
C. mrigala	3.21 ± 0.54	11.25 ± 3.65	2.37 ± 0.21	1.32 ± 0.32	0.35 ± 0.11
C. reba	0.58 ± 0.09	13.25 ± 1.22	3.89 ± 0.41	0.32 ± 0.07	0.28 ± 0.03
C. catla	7.87 ± 2.58	15.24 ± 2.04	2.03 ± 0.11	0.65 ± 0.02	1.08 ± 0.06
L. rohita	3.88 ± 0.15	25.36 ± 2.04	1.12 ± 0.03	0.65 ± 0.1	0.84 ± 0.05
C. latius	1.27 ± 0.07	11.24 ± 0.91	1.27 ± 0.31	0.34 ± 0.6	1.2 ± 0.22
C. garua	0.59 ± 0.04	18.34 ± 1.99	2.22 ± 0.22	0.52 ± 0.02	0.44 ± 0.03
M. tengara	2.09 ± 0.14	21.45 ± 2.91	1.45 ± 0.06	0.39 ± 0.08	0.68 ± 0.07

Gill and liver measurements are separate organ-specific findings. The abstract misassigns the 32.41 µg/g zinc result and the 4.77 µg/g lead result; Table 4 places them in L. rohita gill and C. reba gill respectively. Liver concentrations are not universally highest across every species and metal.

Methods (brief)

The study reports 60 water samples and an ambiguous total of 28 fish samples. Species-level sample-count ranges in Table 1 do not resolve the fish denominator. Filtered water was acid-digested; fish methods describe digestion of 5 g of dry tissue. Atomic absorption spectrometry measured copper, zinc, lead, cadmium and unspeciated chromium. Reported spike recoveries were 96.54–98.85%; numerical detection and quantitation limits were not supplied.

Evidence fitness

The water table supports geographic environmental comparisons. Fish muscle summaries provide qualified freshwater-food occurrence, while gills and liver provide tissue-distribution context. Chromium was not speciated. The paper’s industrial-source explanations are hypotheses without measured source apportionment.

Limitations

Table 4’s wet-weight label conflicts with the dry-tissue protocol; the stated generic conversion factor does not establish how each table was converted. One gill-copper SD is malformed. Fish counts and collection provenance require clarification before pooling. An earlier Ganga study by the authors covered a different species set; possible overlap of its rohu samples has not been resolved.

The exposure table appears to use averages across organs despite a muscle-only methods claim. Its intake-rate units, reference-dose units and several decimal entries are inconsistent. Bioconcentration indices also contain arithmetic discrepancies. These calculations cannot support the paper’s reassurance about consumption safety or its separate carcinogenic-risk assertion. Regulatory comparators are secondary citations, not verified primary instruments.

Fish — freshwater (tilapia, catfish, trout) · Catfish · Aquatic bioaccumulation of heavy metals · Source attribution and environmental burden apportionment · Copper · Zinc · Lead · Cadmium · Chromium

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