Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was studied?
This original research examined how industrialization influences heavy metal (HM) contamination, antibiotic presence, and the dissemination of antibiotic resistance genes (ARGs) in wastewater, sewage sludge, and river water. The study compared two wastewater treatment plants (WWTPs) located in regions of Poland with contrasting industrial development—Silesia (highly industrialized) and Warmia-Mazury (low industrialization). The researchers used quantitative PCR, ICP-OES, and hydride generation atomic absorption spectroscopy to quantify six HMs and nine ARGs across multiple sample points. The study’s primary goal was to identify whether industrialization amplifies selective pressures that promote antibiotic resistance via co-selection mechanisms between metals and antimicrobial compounds, providing insight critical for regulatory frameworks such as heavy metal certification programs.
Who was studied?
The research focused on environmental microbial communities in Polish wastewater ecosystems. Samples were taken from WWTPs in Silesia (industrial) and Warmia-Mazury (non-industrial), including raw wastewater, treated effluents, sewage sludge, and adjacent river water collected upstream and downstream of discharge sites. The microbial DNA extracted represented diverse bacterial populations exposed to industrial and municipal effluents. This community-level approach allowed the assessment of environmental reservoirs of ARGs and integrons under varying pollution and industrial pressure levels, reflecting how anthropogenic contamination shapes microbial resistance dynamics relevant to public health and environmental monitoring.
Most important findings
| Critical Points | Details |
|---|---|
| Higher HM contamination in industrial regions | Silesian WWTP (industrial) showed significantly elevated concentrations of Zn, Pb, Ni, Cr, and As in both liquid and sludge samples compared to the non-industrial Warmia-Mazury plant. Maximum sludge levels exceeded 1000 mg/kg dry mass for Zn, highlighting strong industrial contribution to metal pollution. |
| ARG prevalence correlated with HM levels | Strong positive correlations were identified between HM concentrations (particularly Cr, Ni, Zn) and ARGs such as sul1, sul2, intI1, and intI2 (r > 0.7, p <0.05). These associations were more consistent than correlations between antibiotics and ARGs, suggesting HMs as dominant co-selective pressures. |
| Antibiotic concentrations and treatment efficacy | Fluoroquinolones (ciprofloxacin, norfloxacin, ofloxacin) were the most abundant antibiotics detected (up to 1179.9 ng/g). Treatment processes reduced antibiotic concentrations by 5–14-fold; however, residual levels persisted in effluents and downstream river water, indicating incomplete removal. |
| Sewage sludge as a hotspot for resistance genes | ARG and integrase gene copy numbers were 2–3 orders of magnitude higher in sewage sludge (up to 10¹² gene copies/g) than in wastewater, confirming sludge as a key reservoir for horizontal gene transfer and potential ARG dissemination into soil when used as fertilizer. |
| Industrialization intensifies co-selection | Network analyses revealed denser correlations between HMs and ARGs in samples from industrial regions, demonstrating that industrial pollution acts as a driver of multi-resistance even in the absence of high antibiotic concentrations. |
| Integrons’ role in gene transfer | Class 1 and 2 integrase genes (intI1 and intI2) were abundant and tightly linked with sulfonamide resistance genes, underscoring their importance in mobilizing ARGs under HM-induced selective pressure. |
| Environmental health risk | Despite effective wastewater treatment, treated effluents increased ARG abundance in downstream rivers by up to one order of magnitude, evidencing the persistence of resistant genes and potential human exposure pathways. |
Key implications
These findings emphasize that heavy metal pollution, not only antibiotic misuse, is a major regulatory concern for antimicrobial resistance control. Regulatory programs like Heavy Metal Tested and Certified (HTMC) should integrate co-selection risk assessment into certification standards. Establishing limits for key metals (Zn, Ni, Cr, Pb) in industrial discharge and sludge can minimize environmental antibiotic resistance propagation. Certification should require regular screening for ARG and integrase gene markers in sludge destined for agricultural use. From an industrial perspective, the research highlights the necessity of upgrading treatment technologies to include metal and genetic pollutant filtration. Research gaps remain in long-term gene transfer monitoring and real-world dose–response modeling for HM-antibiotic co-selection in diverse industrial systems.
Citation
Hubeny J, Harnisz M, Korzeniewska E, Buta M, Zieliński W, Rolbiecki D, Giebułtowicz J, Nałęcz-Jawecki G, Płaza G. Industrialization as a source of heavy metals and antibiotics which can enhance the antibiotic resistance in wastewater, sewage sludge and river water. PLOS ONE. 2021;16(6):e0252691. doi:10.1371/journal.pone.0252691
Heavy metals are high-density elements that accumulate in the body and environment, disrupting biological processes. Lead, cadmium, arsenic, mercury, nickel, tin, aluminum, and chromium are of greatest concern due to persistence, bioaccumulation, and health risks, making them central to the HMTC program’s safety standards.
Nickel is a widely used transition metal found in alloys, batteries, and consumer products that also contaminates food and water. High exposure is linked to allergic contact dermatitis, organ toxicity, and developmental effects, with children often exceeding EFSA’s tolerable daily intake of 3 μg/kg bw. Emerging evidence shows nickel crosses the placenta, elevating risks of preterm birth and congenital heart defects, underscoring HMTC’s stricter limits to safeguard vulnerable populations.
Lead is a neurotoxic heavy metal with no safe exposure level. It contaminates food, consumer goods and drinking water, causing cognitive deficits, birth defects and cardiovascular disease. HMTC’s rigorous lead testing applies ALARA principles to protect infants and consumers and to prepare brands for tightening regulations.
