Long-Term Heavy Metal Bioaccumulation in Sprat (Sprattus sprattus) from the Romanian Black Sea: Ecological and Human Health Risks in the Context of Sustainable Fisheries

Abstract

This study evaluates the heavy metals concentrations in sprat (Sprattus sprattus, Linnaeus, 1758) from the Romanian Black Sea, assessing both ecological implications and human health risks associated with consumption. Using long-term data spanning 1994–2019, levels of copper (Cu), cadmium (Cd), lead (Pb), nickel (Ni), and chromium (Cr) in dorsal muscle tissues were analyzed to identify contamination trends and episodic pollution events. Although most concentrations remained below regulatory thresholds, occasional exceedances of Cd and Pb suggest intermittent pollution inputs. Health risks were assessed using dietary indices including estimated daily intake (EDI), target hazard quotient (THQ), total hazard quotient (TTHQ), and carcinogenic risk index (CRI). Findings indicate that, under current exposure levels, regular sprat consumption poses minimal risk. However, prolonged intake during peak contamination periods may contribute to cumulative toxic effects, with implications for ecosystem stability and food safety. Given the persistence of heavy metals and their interactions with co-occurring pollutants, such as persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs), ongoing monitoring remains essential. This study supports the development of sustainable environmental policies aimed at protecting marine biodiversity and consumer health in the Black Sea region.

1. Introduction

The Black Sea is a crucial marine ecosystem that sustains biodiversity and provides essential resources for coastal communities. Among its key species, small pelagic fish such as sprat (Sprattus sprattus) play a fundamental role in the trophic network (Figure S1) and are of significant economic value to commercial fisheries, including those in Romania [1,2,3]. Due to widespread distribution, high mobility, and trophic position, sprat can serve as a bioindicator species for assessing pollutant transfer in marine environments [4,5,6]. Its ability to accumulate heavy metals from both water and prey makes it a valuable species for monitoring contamination trends and potential risks to both marine life and seafood consumers [7]. This species exhibits well-defined seasonal migration patterns, moving towards nearshore areas when water temperatures reach 7–8 °C and retreating to deeper waters during summer. It spawns in winter and primarily feeds on zooplankton, larvae, mollusks, and phytoplankton [8,9].

Historically, this species was a primary target of Romanian Black Sea fisheries, but catch levels have experienced substantial fluctuations, with notable declines since the 2000s due to overfishing, limited fishing seasons, and seasonal variability (Figure S2) [10]. Since the 1990s, Turkey has dominated Black Sea sprat fisheries [11], while in Romania, the underdeveloped fishing fleet, coupled with high operational costs and administrative constraints, has limited its exploitation. Recent studies highlight that, despite a decline in catches over time, sprat remains the dominant species in pelagic trawling along the northern Romanian coast, emphasizing its ecological and economic significance [12].

Human-induced activities, including industrial effluents, agricultural runoff, urban wastewater discharge, and maritime operations, significantly contribute to heavy metal (HM) contamination in the marine environment [13]. These pollutants are persistent, toxic, and bioaccumulative, posing risks to both marine ecosystems and public health. Once introduced, HMs accumulate in the food web, potentially disrupting fish reproduction and development, with cascading effects on higher trophic levels, including human consumers [10,14]. The accumulation of toxic metals in marine fish raises environmental and human health concerns due to their potential for biomagnification within aquatic food chains [15]. Small pelagic fish, particularly sensitive to anthropogenic pollution, serve as bioindicators of marine contamination. Their feeding habits, primarily relying on plankton, may contribute to higher HM accumulation, as planktonic organisms can readily absorb and transfer metals through the food web [16]. The extent of HM uptake and retention in fish is influenced by metal properties, environmental conditions, and species-specific traits, all of which have implications for ecosystem health and human exposure risks [17]. For instance, exposure to HM has been associated with adverse health effects, including neurotoxicity, developmental impairments, and carcinogenic potential [18].

Toxicological risk indicators, such as estimated daily intake (EDI), target hazard quotient (THQ), total target hazard quotient (TTHQ), and carcinogenic risk index (CRI), are widely used to evaluate human exposure risks from seafood consumption [19,20,21]. These indices have been extensively applied in various marine regions, including the Mediterranean [22,23,24], Baltic [25,26,27,28], and Asian seas [29,30,31,32], as well as the Black Sea, particularly in Turkish waters [33,34,35,36], to assess contamination trends and consumer risks. However, similar studies remain scarce for the Romanian waters, particularly for small pelagic fish, such as sprat. This study addresses this gap by integrating fish tissue metal concentration data with quantitative risk assessment to evaluate long-term trends and potential risks associated with fish consumption.

Previous studies into HM contamination in mollusks and fish from the Romanian coast have predominantly addressed tissue concentration levels and spatial-temporal variations in pollutant concentrations [37,38,39]. However, these studies did not assess the implications for human health associated with fish consumption, and the potential consequences remain insufficiently explored, despite the dietary relevance of these species. Recently, a study evaluated the health risks associated with wild mussel (Mytilus galloprovincialis) consumption in Romania [40], highlighting the need for a broader assessment of seafood safety. Building on this approach, the present study represents a comprehensive application of dietary risk assessment indices (EDI, THQ, TTHQ, and CRI) to evaluate potential risks from long-term small pelagic fish consumption in Romania. Although this research focused only on toxic metals, it is important to mention that the presence of co-occurring contaminants, such as persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs), detected in marine biota [41], further complicates risk assessments. These factors underscore the necessity of an integrated evaluation approach to better understand the implications for consumer health.

In Romania, recent studies have addressed the implications of HM contamination in fish in relation to both environmental quality and consumer health. Simionov et al. (2020) [42] evaluated potential health risks associated with the consumption of fish from an aquaculture system located near an industrial area in Galați, reporting that EDI values for HMs such as Pb, Cd, Zn, and Cu were below international safety thresholds. While no immediate risk to consumers was identified, the study highlighted the need for continued monitoring in areas exposed to industrial activities [42]. Building on this, Simionov et al. (2021) [43] proposed an integrated monitoring framework using fish as bioindicators along with oxidative stress (OS) biomarkers—such as MDA, SOD, GPx, and CAT—to predict HM concentrations in tissues from the Danube River, Danube Delta, and Black Sea. Their findings indicate that such bioindicator-based approaches can serve as cost-effective and sensitive tools for detecting pollution trends and assessing ecological and public health risks. These efforts contribute to a broader strategy aimed at ensuring the sustainability of aquatic food resources and safeguarding human health [43].

This study examines long-term variations in the concentrations of HM (Cu, Cd, Pb, Ni, Cr) in sprat (1994–2019), evaluates contamination exceedances, and quantifies human health risks using dietary exposure indices. This species was chosen due to its ecological and economic relevance [44,45], making it a valuable indicator of environmental contamination. Although certain segments of these data have been previously reported in studies addressing HMs concentrations in various mollusk and fish species [46,47], this research constitutes the first application of quantitative risk assessment indices to this dataset to estimate potential risks linked to marine fish consumption in Romania.

Our research explores whether long-term HM accumulation in sprat (Sprattus sprattus) from the Romanian Black Sea reflects historical anthropogenic pollution and whether the declining trends observed toward the end of the study period indicate the impact of improved environmental management. It also examines the potential health risks associated with sprat consumption, particularly during periods of elevated contamination, and assesses whether these risks decreased over time. By integrating bioaccumulation trends with dietary risk indices, the study aims to provide insights relevant to seafood safety and sustainable fisheries policies.

This study focuses on evaluating temporal trends and associated human health risks through fish consumption. Given the ecological and economic importance of small pelagic species in marine food webs and international seafood markets, as well as the transboundary nature of pollution in semi-enclosed seas such as the Black Sea, the findings have broader relevance beyond the national context. By applying standardized toxicological risk assessment indices, this study contributes to the growing body of international research aimed at ensuring seafood safety, supporting environmental protection, and informing regional policy decisions in marine and coastal management.

By integrating tissue metal concentration data with quantitative exposure assessment, the study provides a more holistic perspective on seafood safety over a 25-year period. Addressing existing research gaps, this study offers critical insights for public health recommendations and environmental management in the Black Sea region. The findings emphasize the importance of long-term monitoring and cumulative impact assessments to support seafood safety regulations and the sustainable management of marine resources.

2. Materials and Methods

2.1. Study Area

The Romanian Black Sea coastline spans approximately 244 km and is subjected to significant environmental pressures from both anthropogenic activities and natural processes. The northern sector receives considerable pollutant loads carried primarily by the Danube River, along with contributions from other major rivers, including the Dniester, Dnieper, and Bug, discharging into the north-western part [48]. In contrast, the southern coastal region experiences contamination derived from industrial operations, urban wastewater, harbor activities, maritime transportation, and intense tourism during summer [49,50]. Collectively, these anthropogenic influences contribute substantially to HM contamination, affecting their bioavailability, uptake, and accumulation in marine organisms inhabiting this coastal area [51].

2.2. Sampling Procedure

Fish samples were collected between 1994 and 2019 using pelagic trawls during regular biannual research expeditions conducted in spring (March–April) and autumn (October–November) as part of long-term monitoring of living marine resources along the Romanian coast. Sampling was carried out across the entire Romanian marine sector through pelagic trawl surveys at depths between 21–45 m (Figure 1). From each catch, composite samples consisting of 10–15 adult sprat individuals (7–10 cm in length) were selected for contaminant analysis. The sampling seasons correspond approximately to the post-spawning (spring) and pre-spawning (autumn) periods, considering that peak spawning activity for this species typically occurs during winter [8]. Over the entire study period, a total of 40 composite sprat samples were analyzed for HM content (Table S1). Sample distribution by year was as follows: 1 sample/year in 2004–2005, 2011, and 2015–2019; 2 samples/year in 2002 and 2014; 3 samples/year in 2003 and 2006; 4 samples/year in 2010 and 2013 (as well as 4 samples across the 1994–1999 period); and 6 samples/year in 2001 and 2012. Following sampling, fish specimens were stored in freezer boxes and transported to the laboratory. Dorsal muscle tissues were carefully dissected using sterilized instruments, freeze-dried, homogenized using an electric grinder, and analyzed according to the recommended methodology [52].

2.3. HMs Analysis

Tissue samples underwent digestion using 10 mL of concentrated nitric acid (HNO₃) in sealed Teflon vessels heated on an electric hot plate at 120 °C. The concentrations of copper (Cu), cadmium (Cd), lead (Pb), nickel (Ni), and chromium (Cr) were measured employing graphite furnace atomic absorption spectrometry (GF AAS) using High-Resolution Continuum Source Atomic Absorption Spectrometry equipment (HR-CS ContrAA 800 G, Analytik Jena, Germany) [51]. Each sample was analyzed in triplicate, and mean values were reported. Detection limits of the method ranged from 0.001 to 0.01 µg/L, depending on the specific HM analyzed. Concentrations of HM in tissues were reported as micrograms per gram wet weight (µg/g ww). Analytical accuracy was verified using standardized quality control procedures [53]. All analyses utilized certified high-purity reagents and glassware to minimize potential external contamination.

2.4. Health Risk Indices

Potential risks associated with consuming fish contaminated by HMs were evaluated using several dietary risk indices, specifically the estimated daily intake (EDI), target hazard quotient (THQ), total target hazard quotient (TTHQ), and carcinogenic risk index (CRI) [36]. These indices integrate fish consumption data, HM concentration levels, and toxicological reference values to provide a comprehensive assessment of possible adverse health outcomes from dietary exposure.

The estimated daily intake

(EDI, mg/kg/day) quantifies potential exposure to HMs based on their concentration in fish and the rate of fish consumption. The EDI was calculated following the formula [54,55]:

EDI (mg/kg/day) = (Cmetal × FIR)/BW

where Cmetal represents the concentration of HM in fish muscle tissues (mg/kg wet weight), FIR indicates the average daily food ingestion rate (kg/day) for fish in Romania, obtained from Food and Agriculture Organization Corporate Statistical Database (FAOSTAT) [56], and BW is the average body weight (assumed as 30 kg for children and 70 kg for adults).

The target hazard quotient (THQ) evaluates noncarcinogenic risk from metal consumption, defined as the ratio between the estimated daily intake (EDI) of a specific metal and its chronic oral reference dose (RfD, mg/kg/day):

THQ = EDI/RfD

RfD values, representing safe exposure limits, are 0.0001 mg/kg/day for Cd, 0.04 mg/kg/day for Cu, 0.02 mg/kg/day for Ni, and 0.003 mg/kg/day for Cr, according to United States Environmental Protection Agency (USEPA) Regional Screening Levels (RSL) [57] and the Risk Assessment Information System (RAIS) [58]. RfD value for Pb is not specified. A THQ value exceeding 1.0 reflects that the EDI surpasses the recommended safe exposure limit, indicating potential noncarcinogenic risks.

The cumulative noncarcinogenic risk from exposure to multiple HMs was evaluated using the total target hazard quotient (TTHQ), computed as the sum of individual THQs:

$$\mathrm{T}\mathrm{T}\mathrm{H}\mathrm{Q}=\sum _{\mathrm{i}=1}^{\mathrm{n}}\mathrm{T}\mathrm{H}\mathrm{Q}\mathrm{i}$$

A TTHQ greater than 1 implies a potential chronic health risk from combined exposure, whereas a TTHQ below 1 indicates no significant risk [59]. Evaluating TTHQ provides insights into cumulative exposure and the interactive effects of multiple metals [60].

Carcinogenic risk associated with HM exposure was assessed using the carcinogenic risk index (CRI), defined by the equation [61]:

CRI = EDI × CSF

where CSF (cancer slope factor, (mg/kg/day)⁻¹) quantifies the incremental lifetime cancer risk from sustained exposure to a particular contaminant [62]. For Pb, a CSF value of 0.0085 (mg/kg/day)⁻¹ is adopted, as specified by the USEPA RSL [57] and the RAIS [58]. CRI values below 10⁻⁶ are considered insignificant, values ranging between 10⁻⁶ and 10⁻⁴ are acceptable or tolerable, and values exceeding 10⁻⁴ indicate significant carcinogenic risk [61].

The data were processed using MS Excel 365, and Statistica (TIBCO Software Version 14.0.1.25) [63].

3. Results

3.1. Distribution of HM Concentrations

The concentrations of five HMs (Cu, Cd, Pb, Ni, Cr) in sprat muscle tissues, measured between 1994 and 2019, exhibited substantial variability, reflecting both temporal fluctuations in environmental exposure and episodic pollution inputs (

Table 1. Concentrations of Cu, Cd, Pb, Ni, and Cr in sprat samples over the study period (1994–2019).

	Valid N	Mean	Median	Minimum	Maximum	25th Percentile	75th Percentile	Coef.Var.	Skewness	Kurtosis
Cu (µg/g ww)	40	3.963	2.147	0.190	32.740	0.953	4.841	143.603	3.739	17.055
Cd (µg/g ww)	40	0.7149	0.093	0.005	4.760	0.029	0.581	180.883	2.159	3.597
Pb (µg/g ww)	40	1.008	0.321	0.003	6.120	0.050	1.390	158.812	2.396	5.361
Ni (µg/g ww)	26 *	1.096	0.282	0.001	12.170	0.014	0.515	235.678	3.692	14.493
Cr (µg/g ww)	21 *	0.2942	0.140	0.001	1.592	0.042	0.300	139.600	2.307	5.085

* Ni and Cr were analyzed starting with 2003 and 2006, respectively.

; Figure 2).

Copper (Cu) concentrations ranged from 0.19 to 32.74 µg/g ww, with a mean value of 3.96 µg/g ww. The distribution was highly right-skewed (skewness = 3.739), with a pronounced kurtosis (17.06), indicating occasional extreme values. Most measurements were below 5 µg/g ww, but sporadic peaks reveal intermittent exposure events. The coefficient of variation (CV) was high (143.60%), highlighting significant temporal variability (Table 1; Figure 2).

Cadmium (Cd) levels varied from 0.005 to 4.76 µg/g ww, with a mean of 0.71 µg/g ww. The distribution showed moderate skewness (2.159) and kurtosis (3.60), indicating sporadic peaks. Although most values remained low, the high CV (180.88%) reflects notable fluctuations likely linked to episodic contamination (Table 1; Figure 2).

Lead (Pb) concentrations ranged between 0.003 and 6.12 µg/g ww, with a mean of 1.01 µg/g ww. The distribution was positively skewed (skewness = 2.396) and leptokurtic (kurtosis = 5.36), with occasional high values. The CV of 158.81% indicates considerable variation over time (Table 1; Figure 2).

Nickel (Ni) concentrations, analyzed from 2003 onward, ranged from 0.001 to 12.17 µg/g ww, with a mean of 1.10 µg/g ww. The dataset was strongly skewed (skewness = 3.692) with high kurtosis (14.49), reflecting infrequent but substantial peaks. The very high CV (235.68%) underscores extreme episodic variability (Table 1; Figure 2).

Chromium (Cr), monitored since 2006, showed concentrations ranging from 0.001 to 1.59 µg/g ww, with a mean value of 0.29 µg/g ww. The distribution was moderately skewed (2.307) with a kurtosis of 5.09 and a CV of 139.60%, indicating some irregular peaks but generally lower variability than other metals (Table 1; Figure 2).

3.2. Temporal Trends

Analysis of long-term data (1994–2019) indicates variability in HM levels in sprat tissues, with some metals showing episodic peaks and others appearing more stable in recent years. These fluctuations likely reflect a combination of localized pollution events, environmental management efforts, and hydrodynamic factors influencing metal bioavailability (Figure 3). Copper (Cu) concentrations show noticeable periodic fluctuations, particularly evident during the mid-2000s, possibly linked to episodic industrial discharges or intensive agricultural runoff, yet the general long-term trend is decreasing. Cadmium (Cd) concentrations show higher values in the earlier part of the study period, followed by a noticeable reduction and stabilization in recent years. The initially elevated Cd levels indicate higher anthropogenic inputs or less stringent environmental regulations. This historical trend in Cd concentrations will be linked with subsequent discussions on toxicological risk indices, as early elevated concentrations potentially imply greater risks during that timeframe. Lead (Pb) exhibits irregular variations characterized by occasional peaks; notably, Pb demonstrates pronounced sharp increases, which could originate from localized pollution events or sediment resuspension processes. Nickel (Ni) also displays intermittent peaks, with a distinct elevation detected during the mid-2010s, suggesting sporadic contamination events or specific environmental alterations. Chromium (Cr) presents fewer fluctuations throughout the study period. The presence of prominent peaks in Cu, Pb, and Ni concentrations during specific years points toward isolated pollution incidents, underlining the necessity for targeted investigations to determine the precise sources and conditions of these episodic increases. These temporal patterns reinforce the need for continuous long-term datasets to detect emerging risks and assess the effectiveness of environmental policies over time.

3.3. Exceedances of Safety Limits

Analysis of cadmium (Cd) and lead (Pb) concentrations between 1994 and 2019 revealed frequent exceedances of the maximum allowable concentrations (MAC) set by the European Commission Regulation (EU 2023/915) for seafood consumption (0.25 mg/kg ww for Cd and 0.30 mg/kg ww for Pb) [64] (Figure 4). Notably, these exceedances for both Cd and Pb were most common during the 1990s and early 2000s, reflecting historical environmental degradation linked to past industrial discharges, intensive agricultural practices, and transboundary pollution carried by the Danube River. Lead (Pb) exceedances were recorded throughout the monitoring period, extending up to 2010, indicating intermittent episodes of contamination. In the recent period, exceedances of both Cd and Pb progressively diminished, likely as a consequence of improved environmental management. Nevertheless, the historical contamination patterns underscore the persistence of legacy pollutants in the Black Sea ecosystem, emphasizing the necessity for continued monitoring and regional cooperation to safeguard seafood quality and marine ecological health. These exceedances highlight the importance of sustained regulatory oversight and timely updates to seafood safety assessments, particularly for vulnerable consumer groups.

3.4. Health Risk Assessment

This study presents a comprehensive evaluation of potential health risks associated with the consumption of Black Sea sprat in Romania, leveraging long-term monitoring data spanning 25 years. A key novelty of this research lies in the integration of toxicological risk indices alongside HMs tissular levels, providing a more complete perspective on human exposure. Unlike previous studies that primarily focused on contaminant concentrations in fish, this analysis calculates and interprets risk indices such as estimated daily intake (EDI), target hazard quotient (THQ), total hazard quotient (TTHQ), and carcinogenic risk index (CRI), offering insights into both contamination trends and potential health implications. These indices annual variations over the period 1994–2019 are presented in Table S1.

To assess dietary exposure, the estimated EDI values were compared against the health-based guidance values (HBGV) established by the European Food Safety Authority (EFSA) [55]. For lead (Pb), both the EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) have defined an HBGV of 0.00063 mg/kg/day [65]. Likewise, the EFSA CONTAM Panel recently updated the tolerable daily intake (TDI) for nickel (Ni) to 0.01300 mg/kg/day, following a request from the European Commission to incorporate new data [66]. For cadmium (Cd), the CONTAM Panel has established a TDI of 0.00036 mg/kg/day [67].

The long-term assessment of estimated daily intake (EDI) and risk indices (THQ, TTHQ, CRI) for sprat consumption revealed consistent temporal patterns in HM exposure risks (Table S1; Figure 5). Among the metals analyzed, cadmium (Cd) posed the highest potential health concern, with EDI values frequently surpassing the EFSA health-based guidance value (HBGV) of 0.00036 mg/kg/day, particularly in children. Notable peaks in Cd exposure (THQ > 1) were recorded during high-risk periods, such as 1994–1999 and 2001, reflecting possible influences from anthropogenic sources, including industrial discharges, agricultural runoff, or sediment resuspension. Lead (Pb) occasionally exceeded its HBGV (0.00063 mg/kg/day), with the most pronounced exceedances occurring in 2001. In contrast, nickel (Ni) concentrations remained consistently below HBGV (0.01300 mg/kg/day) throughout the study period. Despite copper (Cu) exhibiting the highest measured concentrations, its contribution to risk indices was negligible due to its relatively low toxicity.

The cumulative risk assessment (TTHQ) reflected these trends, with notable fluctuations over time, emphasizing periods of increased exposure risk (Table S1; Figure 5). TTHQ values exhibited a strong correlation with Cd concentrations rather than the total HM burden (Figure 5). This highlights the predominant role of Cd toxicity in driving cumulative health risks. Despite higher measured concentrations of metals such as Cu or Ni, their lower toxicological impact resulted in a minimal contribution to cumulative risk indices. The potential risks associated with fish consumption were influenced by a combination of HM toxicity and food ingestion rate (FIR). In children, the higher FIR relative to their lower body weight led to elevated EDI, THQ, and TTHQ values, substantially increasing risk levels compared to adults. During peak contamination years, frequent exceedances of the acceptable cumulative risk threshold (TTHQ > 1) were noticed. While adults generally exhibited lower risk levels, occasional exceedances approached the threshold, particularly during periods of elevated Cd exposure (Table S1; Figure 5).

The CRI for Pb remained well below the acceptable threshold (10⁻⁶–10⁻⁴), indicating the minimal long-term carcinogenic risk associated with its consumption (Table S1; Figure 6). These findings indicate that while Pb occasionally contributed to noncarcinogenic risks through elevated EDI values, its overall carcinogenic potential was negligible. Periods of elevated Cd exposure coincided with increased anthropogenic pressures, underscoring the necessity for stricter regulatory controls on industrial and agricultural discharges, as well as enhanced sediment management measures. Given the risk dynamics associated with Cd, dietary recommendations should consider limiting fish consumption for high-risk groups, during contamination peaks. Public health initiatives should focus on raising awareness of HM exposure risks while promoting the safe and sustainable consumption of seafood. These findings provide an evidence-based foundation for refining seafood consumption guidelines and developing targeted risk communication strategies in the region.

4. Discussion

The analysis of Cu, Cd, Pb, Ni, and Cr in Sprattus sprattus from the Romanian Black Sea (1994–2019) revealed substantial variability, including sporadic spikes likely associated with localized contamination. Elevated levels, particularly during the 1990s and early 2000s, appear to reflect legacy pollution combined with complex environmental factors affecting contaminant behavior [68]. Possible explanations for these observed trends include extensive industrialization and intensive agricultural practices during the communist era, leading to prolonged ecological degradation and pollutant accumulation in marine ecosystems even after the collapse of these sectors following the fall of communist regimes in the late 1980s [69]. The Danube River, as a significant input pathway into the Black Sea, carried substantial nutrients and hazardous substances loads originating from its industrialized and agriculturally intensive watershed [70]. Additionally, the Yugoslav conflicts and associated NATO airstrikes on industrial facilities during the 1990s exacerbated pollutant inputs into the Danube River and subsequently the Black Sea [71,72]. Although Romania also experienced a reduction in industrial activities and intensive agriculture, ecological recovery remained slow due to persistent contaminants in sediments, inadequate wastewater management, and the semi-enclosed characteristics of the Black Sea basin. A significant improvement emerged following Romania’s accession to the European Union in 2007, marked by the adoption of comprehensive EU environmental standards and substantial investments in wastewater infrastructure, sustainable agricultural practices, and industrial upgrades [73]. Nevertheless, isolated incidents, including extreme meteorological events or upstream contaminant releases, occasionally led to temporary elevations in hazardous substances, reflected in fluctuating concentrations within marine biota.

No consistent upward trends were noted during the study period; however, fluctuations in metal concentrations—especially for Cd and Pb—were notable, with occasional exceedances of regulatory limits. These patterns reveal that the marine environment remains vulnerable to episodic pollution events. In contrast, Ni and Cr levels were relatively stable over time.

These findings align with contamination trends reported in other enclosed and semi-enclosed marine systems. For instance, a study on the HM levels in herring, sprat, and cod from the southern Baltic Sea during the years 1994 to 2003 revealed significant downward trends in HM accumulation, particularly for Pb, Hg, and Cd across all species [4]. The findings indicate improvements in the marine environment of the southern Baltic, likely due to reduced inputs from river discharges and atmospheric deposition [4]. Studies in the Mediterranean and Baltic Seas have shown that HM levels in marine ecosystems exhibit variability over time, influenced by both natural processes and anthropogenic pressures [74,75,76]. While regulatory measures and improved wastewater management have contributed to reductions in some regions, episodic pollution events continue to occur due to legacy contamination, riverine inputs, and sediment resuspension [77,78,79,80]. Similar assessments in Turkish Black Sea waters indicate that HM concentrations in pelagic fish follow comparable patterns, though species-specific differences and local pollution sources influenced variability [35]. The comparison underscores the importance of long-term monitoring across different marine regions to assess seafood safety and evaluate the effectiveness of pollution mitigation efforts.

Sprat is a pelagic fish, but it frequently dives into deeper waters; thus, its ecological role and contaminant exposure are shaped by feeding behavior and habitat preferences [81]. Unlike surface-dwelling filter feeders, sprat undergoes diel vertical migrations, foraging at varying depths where it encounters contaminants from both water and prey [82]. This movement pattern increases its exposure to pollutants originating from different sources, including sediment-associated contaminants, contributing to the observed variability in HM content. Its feeding strategy and thermal preferences also influence its response to environmental stressors [83]. Unlike benthic species that accumulate metals primarily from sediments, pelagic fish such as sprat integrate pollutants through both direct water exposure and trophic interactions [84]. The sensitivity of small pelagic fish to episodic pollution events reflects their potential as bioindicators for detecting acute environmental changes [85]. Fluctuations in HM concentrations in sprat tissues likely result from periodic pollution events and broader ecosystem shifts. These findings underscore the importance of long-term monitoring of pelagic species to track contaminant trends and ensure seafood safety in the Black Sea.

HM accumulation in marine fish presents both ecological and public health concerns, as these contaminants can disrupt biological processes, reduce reproductive success, and contribute to ecosystem imbalances [86,87]. Their persistence in marine environments means that contamination risks remain significant even after primary sources of pollution decline [88]. The ingestion of contaminated seafood represents a key pathway for human exposure, with potential long-term health effects, particularly in regions experiencing ongoing pollutant discharge and where fish consumption is high [89,90].

The present study reinforces previous findings that emphasize the importance of continuous monitoring to assess temporal patterns of metal concentrations in commercially important fish species. Investigations on Mugil auratus from Turkish waters revealed seasonal fluctuations in Cu, Pb, and Cd levels, with partial compliance with regulatory thresholds [91]. Variability in species-specific metal uptake has also been noted in Merlangius merlangus, Mullus barbatus, and Engraulis encrasicolus from the Black Sea and Mediterranean, reflecting regional pollution inputs and biological differences in metal assimilation [92]. A broader assessment of fish from the Turkish Black Sea coast reported metal concentrations below daily intake limits but underscored the need for long-term surveillance to identify potential risks [93]. Further studies indicate that HM tend to accumulate more in non-muscle tissues, reducing direct dietary exposure through fillet consumption but not eliminating health concerns. Stricter environmental policies implemented after 2006 have likely contributed to declining contamination trends and improved seafood safety [94]. However, the presence of periodic exceedances and the potential for localized contamination highlight the necessity of sustained regulatory oversight and pollution mitigation strategies to minimize environmental and public health risks.

Studies on commercially significant fish species from the Black Sea indicate that HM accumulation generally remains within international safety limits, posing minimal risks for the general population. Species-specific variations in metal accumulation have been documented, with levels differing by location but largely falling within tolerable intake thresholds [6]. Research on Trachurus mediterraneus ponticus and Engraulis encrasicolus indicated that both carcinogenic and noncarcinogenic risks remain within safe margins. However, continued monitoring is advised due to potential shifts in environmental contamination patterns [95,96].

Long-term assessments (2009–2019) of key commercial species from the southern Black Sea demonstrated stable contaminant levels, reflecting the effectiveness of regulatory pollution controls [35]. Findings from the Eastern Black Sea further corroborate that estimated daily intake and target hazard quotients do not indicate significant noncarcinogenic risks [34]. Additional studies on fish from Turkey, Georgia, and Abkhazia [33], as well as investigations on Merlangius merlangus, Mullus barbatus, and Trachurus mediterraneus from the Turkish Black Sea [15], reinforce these conclusions. Despite the overall low risk, specific populations, such as children and frequent seafood consumers, may experience slightly higher exposure levels [15]. These findings highlight the importance of sustained surveillance to account for potential contamination fluctuations and ensure long-term food safety in the Black Sea region.

This study provides valuable insights into HM contamination in Black Sea fish and its potential implications for consumer health. The persistence of certain metals in marine organisms highlights the need for continuous monitoring to safeguard food safety, as some species may accumulate elevated concentrations, posing potential health concerns [17]. Ongoing research is crucial to assess contamination trends over time and develop effective mitigation strategies to minimize exposure risks. Our findings reveal temporal fluctuations in Cu, Cd, Pb, Ni, and Cr concentrations, with no consistent increasing trend over the study period. However, periodic exceedances of Cd and Pb, particularly during the 1990s and early 2000s, reflect contamination linked to industrial discharges and agricultural runoffs. These episodic peaks emphasize the role of anthropogenic activities in influencing HM distribution and accumulation patterns in marine ecosystems. Given the potential health risks, particularly for vulnerable groups such as children and frequent fish consumers, these results reinforce the necessity of sustained environmental monitoring and regulatory controls. Strengthening pollution management strategies and enforcing stricter discharge regulations can further mitigate HM contamination, ensuring the long-term safety of seafood resources in the Black Sea region.

The implementation of stricter environmental regulations, particularly after Romania’s accession to the European Union in 2007 [44], has played a significant role in reducing HM contamination in recent years. This decline is consistent with findings from other Black Sea studies, which have reported decreasing metal concentrations and lower ecological risks due to enhanced pollution control measures and improved wastewater treatment systems [35].

Our toxicological risk assessment based on EDI, THQ, TTHQ, and CRI indices indicates that current metal levels in fish pose minimal to negligible risks for consumers. However, historical exceedances of cumulative hazard indices underscore the need for continued environmental monitoring and proactive public health strategies. Comparative studies indicate that the risks associated with fish consumption have declined compared to earlier decades when anthropogenic pressures were higher [92,94], reflecting broader regional progress in pollution management. Despite the overall reduction in health risks, Cd remains a key contributor to cumulative exposure indices. Elevated Cd levels recorded in earlier years highlight the necessity of sustained monitoring and targeted mitigation efforts. Given the significant role of sprat in commercial fisheries, these findings emphasize the need for routine contaminant assessments in fish stocks to ensure consumer safety and compliance with international regulatory limits. Strengthening pollution control policies and refining seafood safety guidelines will be essential to ensuring long-term consumer protection and maintaining environmental quality in the Black Sea region.

Although this research is based on data collected up to 2019, the conclusions regarding seafood safety are supported by the downward trends in HM concentrations observed in the latter part of the monitoring period, reflecting the state of the environment at that time. These trends are supported by similar studies conducted in the region, which have reported improvements in water quality and reductions in contaminant loads following the implementation of stricter environmental policies [35,51,73,94]. Furthermore, long-term assessments in the Black Sea region also indicate lower contaminant levels in marine fish species after 2015 [15,33,34,95,96], confirming broader regional progress. Nonetheless, it is important to emphasize that environmental conditions in the Black Sea remain dynamic. Emerging pressures, including those associated with recent geopolitical conflicts and industrial disruptions in the region, may alter pollutant inputs and affect marine ecosystem health [97,98]. Therefore, this study also aims to raise awareness of the urgent need for continued monitoring and updated assessments of contaminant levels in fish. Ensuring long-term seafood safety and ecosystem protection requires regular data collection, particularly in light of changing environmental and political conditions that could reverse previous improvements.

This study has several limitations that should be considered. The analysis did not establish direct correlations between HM content and specific anthropogenic sources or geographic distribution patterns, which could provide more targeted insights into contamination drivers. Additionally, other environmental contaminants, such as persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs), were not included in the assessment, despite their potential interactions with HMs, which may amplify both ecological and human health risks [99]. Another limitation is the absence of specific dietary intake data for different population groups, which restricts the precision of toxicological risk evaluations.

While regular marine monitoring in Romania collects annual data on seawater, sediments, and mollusks, recent data on pollutants in fish remain scarce. This gap is particularly relevant in the context of the Marine Strategy Framework Directive (MSFD) [100], specifically Descriptor 9 (D9), which addresses contaminants in seafood and their potential risks to human health. Despite financial constraints preventing the inclusion of fish in routine monitoring efforts, obtaining updated data on metal concentrations in commercially important fish species remains crucial for accurate risk assessments.

Overall, our results underline the necessity of integrating fish contamination monitoring into national marine surveillance programs to provide seafood safety guidelines for fisheries management. Establishing consumption advisories based on periodic HM assessments would support both public health recommendations and sustainable fisheries policies in the Black Sea.

Future research should prioritize spatial analyses to identify localized pollution sources, expand contaminant monitoring to include various species of marine fish, and incorporate dietary patterns to refine seafood safety evaluations. A key knowledge gap remains in understanding the cumulative effects of HMs, POPs, and PAHs, as their potential additive or synergistic toxicity is not yet fully characterized [101]. To address this, integrated risk assessments that consider multiple contaminants simultaneously are necessary to provide a more comprehensive evaluation of seafood safety in the Black Sea region.

5. Conclusions

This study provides a long-term assessment (1994–2019) of HMs contamination in sprat (Sprattus sprattus) from the Romanian Black Sea. In recent years, metal concentrations (Cu, Cd, Pb, Ni, Cr) have generally remained within international safety thresholds, suggesting minimal health risks associated with consumption. However, elevated levels of Cd and Pb recorded in the 1990s and early 2000s indicate potential past exposure concerns, especially for high-frequency consumers and sensitive population groups.

The decline in contamination levels in later years highlights the positive impact of regulatory measures and improved wastewater management. Toxicological risk indices (EDI, THQ, TTHQ, CRI) support the conclusion that current risks are low. Nevertheless, historical exceedances—particularly for Cd—emphasize the need for continued environmental surveillance and targeted mitigation strategies.

The results of this study support the premise explored. Historical data confirm that sprat experienced elevated cadmium and lead levels, particularly during the 1990s and early 2000s, consistent with legacy pollution sources. Toward the latter part of the monitoring period, a noticeable decline in contaminant levels and associated health risk indices reflects the positive effects of environmental regulation and improved wastewater management. These findings highlight both the persistence of historical contamination and the encouraging outcomes of sustained pollution control efforts.

Given the ecological and commercial significance of marine fishes, routine contaminant assessments are essential to ensure food safety and regulatory compliance. Future efforts should incorporate spatial analysis, integrate additional contaminants such as POPs and PAHsinto cumulative toxicological risk assessments, and refine dietary exposure models to enhance public health recommendations and inform sustainable fisheries management in the Black Sea region.