1 Introduction

While the presence of pharmaceutical residues in the environment has been recognized for some time, recent advances in detection methods, along with new toxicological insights and their non-regulatory status, have heightened concern. These residues have been detected in various environmental compartments, including wastewater, groundwater [1], surface water [2] as well as drinking water [3], often at very low concentrations ranging from ng/L to µg/L. Various factors have been suggested to contribute to the ever-increasing presence of pharmaceuticals in the environment. These factors include an increase in the prescription and consumption of pharmaceuticals for various therapeutic purposes, the use of pharmaceuticals in animal husbandry for the treatment and prevention of veterinary diseases and their use as growth promoters, and the general practice of improper disposal methods for unused and expired medications. Various pharmaceuticals, including antibiotics, anti-inflammatory drugs, anti-histamines, antimicrobials, hormones, β-blockers, and anti-epileptics, have been identified in influents and effluents of wastewater treatment plants, aquatic environments, water resources, and vegetables worldwide [4].

Pharmaceutical contaminants enter the environment via a variety of routes, including discharge of effluents from municipal and hospital wastewater treatment plants, direct excretion into water or land by humans or animals, land fertilization using animal manure, and the use of antibiotic soaps for bathing [5]. Disposal of pharmaceuticals as part of the waste generated in households into dumpsites and landfills is another major route by which pharmaceuticals get into the environment [6]. Pharmaceuticals and their metabolites have high polarity and moderate-to-low volatility, making them easily transported and dispersed in water bodies [7]. Once they enter the environment, a portion of the pharmaceutical contaminants usually get degraded, however, a large amount persists in the environment [8].

Pharmaceutical products are generally designed to elicit specific responses from precise biological targets. As such, their effects on the environment are largely unknown and likely undesirable. There is a growing worry about the possible human and ecosystem health effects due to the presence of pharmaceuticals and their metabolites in the environment [9]. The emergence of antibiotic-resistant bacteria strains as a result of continuous exposure to low doses of antibiotics represents a major global concern [10]. Antibiotic resistance genes can develop in the environment if antibiotic residues are present and these genes can then be transferred to pathogenic bacteria. Resistance genes can be exchanged between environmental bacteria and clinical strains [11]. Even at low concentrations (around ng/L), hormones could have adverse impacts on reproductive and sexual development, like the feminization of male fish [12]. Pharmaceuticals in the environment may therefore have significant effects on aquatic life in particular, and the ecosystem in general.

In Ghana, different classes of pharmaceuticals have been detected in several environmental matrices at varying concentrations. Some antibiotics such as cefuroxime, ciprofloxacin, erythromycin, sulfamethoxazole, and trimethoprim have been detected in lettuce obtained from markets in Kumasi and its environs [13]. Various antibiotics (β-lactams, tetracyclines, chloramphenicol, macrolides, aminoglycosides, sulfonamides, and quinolones) at levels above recommended maximum residual limits have also been detected in meat, dairy, and fish products on the Ghanaian market as well [14]. Amoxicillin, chloramphenicol, diclofenac, metronidazole, and paracetamol have also been detected in two major reservoirs (Barekese and Owabi in the Ashanti region) that provide water for a large population in Ghana [2]. The occurrence of pharmaceuticals in the environment could be associated with population density, level of income, age (elderly people with chronic health crises), and presence of pharmaceutical companies in the catchment area amongst others [7].

Recent studies on the fate of unwanted or expired medications in Ghana indicated that they are improperly discarded along with household waste in dustbins for onward disposal at landfill sites [15]. It has also been reported that some pharmacies and over-the-counter medicine sellers use dumpsites and landfills to dispose of unused and expired medications [16]. The occurrence of pharmaceutical residues in leachate and soil of landfills and dumpsites in Ghana is sparingly documented. A study by Borquaye has shown the presence of antibiotics and antibiotic-resistant bacteria in leachate and soil samples from landfills and dumpsites within Kumasi [17]. Another study also reported the occurrence and ecological risk of analgesic and antibiotic residues in leachate and soil from dumpsites in the Sunyani municipality of Ghana [18].

Ejisu-Juaben, a municipality with a population density of approximately 180,723, constituting 33.22% of the Ashanti Region [19], is characterized by a high concentration of pharmaceutical companies, pharmacies, and over-the-counter-medicine sellers. Despite these factors, there is a lack of studies on the area’s pharmaceutical residues in landfills and dumpsites. This study investigates the presence and ecotoxicological risks of pharmaceutical residues at dumpsites in Ejisu-Juaben. Additionally, it examines household and pharmacy disposal practices for unused and expired medications. The distinct socio-economic, demographic, and environmental characteristics of Ejisu-Juaben offer a unique perspective on pharmaceutical use and disposal patterns. While previous research has addressed pharmaceutical contamination in larger cities such as Kumasi and Sunyani, this focused regional approach provides valuable insights into the specific challenges and dynamics of Ejisu-Juaben. This enhances local understanding and contributes to the global comprehension of pharmaceutical contamination in diverse geographical settings. The study's findings will contribute to bridging the knowledge gap on environmental loads of drug residues, informing policies for the safe use and disposal of medicines both locally and globally.

2 Materials and methods

2.1 Study area

The Ejisu-Juaben municipality is one of the 30 administrative and political districts in the Ashanti Region of Ghana [20]. The municipality’s vegetation has been classified as a semi-deciduous forest zone, characterized by a combination of deciduous and evergreen plant species. The rainfall in the area follows a bi-modal pattern, with the major rainy season occurring from March to July and a minor rainy season from September to November. The average annual rainfall in the district is approximately 1200 mm. Additionally, the average temperatures typically range between 20 °C and 32 °C, with August being the coolest month and March being the warmest [21]. It is globally known for its rich cultural heritage and tourist attractions, especially the booming kente weaving industry. The population of the Municipality was about 180,723 as of 2021 and this represents 33.22% of the region’s total population. The people in the municipality engage in a variety of occupations including trading, crop and animal farming, and factory workers, amongst others [21]. The most widely used method of solid waste disposal by the populace within the study area is dumping in the open space, according to the 2021 Population and Housing Census [19]. A map of the study is shown in Fig. 1.

Fig. 1
figure 1

Map of Ejisu-Juaben Municipality showing the sampling points

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2.2 Survey on disposal of pharmaceuticals

To investigate the routes used to dispose of unused and expired medications in the municipality, a survey of about 400 households in the Ejisu-Juaben Municipality was conducted. The sample size of household respondents was determined using Andrew Fisher's formula, which is represented by Eq. 1:

$${\text{sample}}\;{\text{size}} = \left( {(z - {\text{score}})^{2} \times \;{\text{Std}}\;{\text{Dev}}\; \times \;(1 - {\text{Std}}\;{\text{Dev}})} \right)/\left(( {{\text{confidence}}\;{\text{interval}})^{2} } \right)$$
(1)

To calculate the sample size, the population size of the Ejisu-Juaben Municipality was initially obtained from the Ghana Statistical Service, which reported a population of 180,723 individuals. At a 95% confidence level and a z-score of 1.96 using a standard deviation of 0.5 [22], the confidence interval was found to be ± 4.90%. Plugging these values into the formula, the sample size was computed as 400. The survey evaluated the general public's level of awareness of the presence of pharmaceutical products in the environment and their knowledge of the possible impact of these pharmaceutical products in the environment. The questionnaire generated socio-demographic data, as well as respondents’ habits regarding the disposal of expired or unused medications and their understanding of the environmental effects of medications. Participants either completed the survey themselves or had their responses marked by the researchers. The data was coded and input into Microsoft Excel 2016. The completeness, consistency, and reliability of the data were all examined. When respondents did not finish a question, it was considered missing values, and only complete answers were utilized to calculate the results. Statistical analysis of the questionnaire responses was performed using SPSS.

2.3 Ethical approval and informed consent

Before their participation, every respondent was asked to sign a consent form, confirming their voluntary involvement in the survey. For participants aged 15–18, consent was obtained from their guardians or parents. The study received ethical approval from our university’s Research Ethics Committee, ensuring that all procedures complied with established ethical standards and guidelines.

2.4 Confidentiality

Participants were assured that all information shared during the survey would be handled with the utmost confidentiality. Their responses and personal information would be securely protected and used exclusively for research purposes. The data collected would be anonymized and reported in aggregate form to maintain the privacy and confidentiality of individual participants.

2.5 Adherence to the declaration of Helsinki

This study was conducted following the ethical principles outlined in the Declaration of Helsinki (http://www.wma.net/en/30publications/10policies/b3/index.html). The research adhered to all applicable guidelines to ensure the safety, rights, and well-being of the participants, including their informed consent and confidentiality.

3 Materials

HPLC-grade chemicals were used throughout the study. Analgesics and antibiotic standards were obtained as pure powders (pure synthetic forms) from Ernest Chemists (Accra, Ghana). Ultra-pure deionized water was used to prepare all the reagents and calibration standards for HPLC analysis. Before HPLC analysis, all solutions and samples were filtered using a microfilter (0.2–0.6 μm). Structured questionnaires were used in a face-to-face interview to assess the disposal route for unwanted and expired medicine.

3.1 Sample collection and handling

Samples were collected from 8 dumpsites in the municipality. Each dumpsite was divided into 4 quadrants, and soil samples (2 samples each) were taken from each quadrant. All soil samples from each dumpsite (8 in all) were mixed to form one composite sample. Leachate samples were collected from each dumpsite and used as such. A total of 16 samples (8 soil and 8 leachate samples) were collected from the 8 dumpsites within the Ejisu-Juaben Municipality: Onwe old site (6°41′20.6″N, 1˚27′41.7’’W), Onwe new site (6°41′19.6’’N, 1°27′036’’W), Akyawkrom (6°44′02.6″N, 1°27′33.1″W), Donyina (6°38′08.1″N, 1°29′36.8″W), Achinakrom (6°39′36.1″N, 1°28′07.7″W), Krapa (6°42′132’’N, 1°27′54.8’’W) and Juabeng (6°47′30.5″N, 1°25′23.0″W). A soil sample from the KNUST Botanical Garden (6°40′28.4″N, 1°34′17.6″W) was used as a control. All soil and leachate samples collected were preserved using ice and immediately transported to the laboratory for analysis.

3.2 Physicochemical parameters

The physicochemical parameters evaluated included the pH, total dissolved solids (TDS), electrical conductivity (EC), and total organic carbon (TOC). About 10 mL of a well-mixed leachate sample was transferred into a clean beaker. The pH, TDS, and EC were then recorded using a Mettler Toledo (Switzerland) pH meter and a multi-parametric probe (WTW, Weilheim Germany). For soil samples, 10% (w/v) of dried pulverized sample to distilled water was prepared for pH and EC analysis. For TOC determination, about 1.0 g of the soil sample was weighed directly into a crucible and heated in an oven at 105 ℃ for 2 h. The samples were removed and cooled in a desiccator and then weighed. The samples were then placed in a pre-heated Thermo Lyne Muffle Furnace at 55 ℃ for 4 h. Samples were cooled, and then weighed. The TOC was determined from Eq. 2:

$$TOC{\text{ }} = \frac{{x - y}}{x} * 100$$
(2)

where x represents the initial weight of the soil sample and y is the final weight of the sample.

3.3 Pharmaceutical residue analyses

3.3.1 Extraction

Leachate samples (1.5 L) were thoroughly mixed and filtered using a Whatman filter paper (0.45 µm pore size) before solid phase extraction (SPE). An HLB cartridge (6 mL, 200 mg, Green Mall, Jiangsu, China) was used for SPE. SPE columns were conditioned using 5 mL of methanol and 5 mL of distilled water. The leachate filtrate was passed through the pre-conditioned cartridges at a flow rate of 1 mL/min. The SPE cartridge was washed with 5 mL of distilled water before elution. Analytical targets were eluted with 2 mL of methanol and 0.1% acetic acid mixture (1:1 v/v), whereas antibiotic analytes were eluted with 2 mL of methanol and a 0.05% trifluoroacetic acid mixture (1:4 v/v).

For soil samples, approximately 10 g of the air-dried, pulverized soil sample was weighed into a clean conical flask, and 100 mL of acetonitrile was added. The mixture was sonicated (VWR, USC 600 T, 45 kHz, 120 W) for 30 min. The supernatant was filtered through a 0.45 μm nylon membrane filter (Whatman, U.K) into another clean flask and subjected to the same SPE protocols described earlier for leachate samples. The eluates were transferred into new containers and analyzed by HPLC [18].

3.4 HPLC analysis

Chromatographic separation of antibiotics and analgesic analytes was done on a Perkin Elmer Flexar HPLC coupled to a PDA detector. Separation of antibiotics was achieved on Agilent Zorbax 300SB C18 (250 × 4.6 mm, 5 µm). The mobile phase comprised 0.05% TFA (solvent A) and methanol (solvent B). Chromatographic separation of analgesic and caffeine analytes was achieved on a Phenomenex Luna C8 column (150 × 4.6 mm, 5 µm). The mobile phase comprised 0.1% acetic acid (A) and methanol (B). As with antibiotic analysis, a flow rate of 1 mL/min was employed with an injection volume of 20 μL. The chromatographic conditions used were the same as described in an earlier work [2]. For antibiotics, amoxicillin, chloramphenicol, ciprofloxacin, doxycycline, and metronidazole were monitored at 215 nm. The detection of paracetamol, caffeine, and diclofenac was at 270 nm, and that of ibuprofen was at 220 nm, as reported earlier [2]. All analyses were done at ambient temperature.

3.5 Quality parameters

The analytes were quantified based on the peak areas using each standard's five-point calibration curves (5–160 ppm). Recovery, linearity, limits of detection, and quantitation quality parameters were the same as those reported earlier [2]. The linearity of each test sample was investigated over the concentration range of 5–160 ppm. The limits of detection (LOD) for each of the reference pharmaceuticals were determined at the signal–noise ratio of 1:3, while the limits of quantitation (LOQ) were determined using a peak signal-to-noise ratio of 1:10.

3.6 Recoveries and quality assurance

A sample blank was spiked with a known amount of standard drug (water and soil matrices devoid of any of the analytes). After the extraction and SPE clean up procedures, the sample blank was examined using the HPLC techniques previously discussed. The chromatograms that were produced were used to determine the drug concentration. Standard analyte solutions were injected to evaluate the performance of the HPLC system before analysis and every ten sample runs. To check for sample interference, blank samples were additionally injected after every 5 runs. There were repeated injections of each sample. Each batch of investigations contained a reagent blank to screen for background interference. The recovery and quality assurance data are displayed in Table 1.

Table 1 Quality parameters
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3.7 Ecotoxicological risk assessment

The guidelines issued by the European Agency for Evaluation of Medicinal Products were used to calculate ecotoxicological risk assessment [23]. The risk assessment is generally expressed in terms of hazard quotient (HQ) as depicted in Eq. 3:

$$HQ = \frac{MEC}{{PNEC}}$$
(3)

where HQ represents hazard quotient, MEC is the minimum measured environmental concentration in (µg/L or µg/kg), PNEC is the predicted no effect concentration (µg/L or µg/kg). The hazard quotient (HQ) is the ratio of a substance's possible exposure to the threshold at which no detrimental effects are anticipated. When HQ values are greater than 1, then the risk is described as high to the organisms. For situations where 0.1 ≤ HQ ≤ 1, a medium risk is presented and an HQ < 0.1 implies a low risk [6]. The PNEC for fish, daphnia, and algae were extracted from the literature [24] and the MEC was the concentration of analytes determined in the study. Classification of risk was based on the Ashfaq’s limits.

4 Results

4.1 Physicochemical properties

Generally, the leachate samples had pH that ranged from neutral to slightly basic (7.84–8.73). The soil samples were slightly acidic to slightly basic (6.38–8.18). The total dissolved solids (TDS) of the leachates were in the range of 30–1479 mg/L whilst that of the soil samples ranged from 1.59 to 13.60 mg/L. Soil samples collected from the dumpsites had electrical conductivity of 1.0–29 µS/cm as against 103–1566 µS/cm for leachate samples. The total organic carbon of the soil samples ranged from 0.40 to 6.54%. Table 2 presents the physicochemical parameters of soil and leachate samples from dumpsites within the municipality.

Table 2 Physicochemical properties
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4.2 Occurrence of analgesics and antibiotics

The linearity of the HPLC method used in analyses was tested for concentrations between 2.5 and 200 µg/mL for both analgesics and antibiotics. The results showed a strong correlation for all the analyzed antibiotics and analgesics, with the coefficient of correlation, R2, values ranging from 0.98 to 0.99. The limits of detection (LOD) and limits of quantitation (LOQ) for all analytes were found to be between 0.031 and 0.116 µg/mL and 0.103 and 0.386 µg/mL, respectively. These values were based on a signal-to-noise ratio of 1:3. The recoveries for the various analytes were all high, ranging from 85.5 to 97.0% (Table 1).

Five out of nine pharmaceutical residues that were analyzed were found in leachate samples collected from the various dumpsites (Table 3). The concentrations of these pharmaceuticals ranged from 0.01 to 74.53 µg/L. The analyte with the highest concentration detected in the leachate samples was chloramphenicol at 74.53 μg/L, followed by doxycycline at 3.67 µg/L, amoxicillin at 1.77 µg/L, diclofenac at 1.20 µg/L, and paracetamol at 0.29 µg/L. Caffeine, ibuprofen, metronidazole, and ciprofloxacin were not detected in any of the leachate samples. All the detected pharmaceuticals were found in over 80% of the samples tested, with chloramphenicol, amoxicillin, diclofenac, and paracetamol being present in all samples tested (100% frequency of detection). The same analytes detected in the leachates were also present in the soil samples collected from the dumpsites (Table 3). The concentrations of the detected analytes in soil samples ranged from 0.06 to 305.06 µg/kg. Amoxicillin recorded the highest concentration (305.06 µg/kg), followed by chloramphenicol (253.46 µg/kg), doxycycline (53.04 µg/kg), diclofenac (25.27 µg/kg) and paracetamol (11.70 µg/kg). Chloramphenicol, diclofenac, and paracetamol were the most frequently detected pharmaceuticals in the soil samples (100%). This was followed by amoxicillin (72.73%) and doxycycline (54.55%). As in the case of leachates, caffeine, ibuprofen, metronidazole, and ciprofloxacin were not detected in the soil samples with the methods used for analyses. Table 3 represents the outcome of the pharmaceutical analyses in the leachate and soil samples.

Table 3 Occurrence of pharmaceutical residues of samples in dumpsites within Ejisu–Juaben municipality
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4.3 Ecotoxicological risk assessment

Results of the ecological risk assessment for the three most dominant organisms used to estimate the impacts of pharmaceuticals in various environmental compartments are presented in Table 4. The hazard quotient (HQ) which estimates the impact level of the risk posed by a contaminant to the living organism was obtained by finding the ratio between the measured environmental concentrations (MEC) and the predicted no-effect concentration (PNEC) of the pharmaceutical residues. The risk was established using the criterion of Ashfaq and coworkers. Generally, the pharmaceutical residues recorded posed low to high risk to all the organisms investigated. The hazard quotient recorded varied considerably from one analyte to another. While the HQ for amoxicillin in leachate.

Table 4 Ecological Risk Assessment of samples from dumpsites within Ejisu – Juaben Municipality
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samples ranged from 0.71 to 1.77, that in the soil samples was 122.02–305.06. Similarly, paracetamol recorded HQ values between 0.12–31.52 and 87.31–1271.74 in leachate and soil samples, respectively. The risk quotient for diclofenac and doxycycline in leachate, (2.26–82.76 and 3.55–36.7) were lower as compared to that of the soil, (47.50–1742.76 and 51.25–530.4) for the same analytes respectfully. Generally, amoxicillin and paracetamol detected in leachate samples posed moderate to high risk to fish as against the other organisms. Almost all the pharmaceuticals present in the leachate samples posed a high risk to all the organisms tested. Similarly, the concentration of pharmaceuticals recorded in the soil samples also showed a greater risk against daphnia and algae.

4.4 Survey

Four hundred (400) respondents participated in this study. The majority of the participants, when asked how often they disposed of unused and/or expired prescription and non-prescription medicines, said they discarded these when they did not need both orthodox (71.0%) and herbal (52.8%) medications. Table 5 summarizes these responses. Additionally, the interviewers read out methods for disposing of unused and expired medicines. The most common disposal technique was via household garbage in dustbins for onward disposal at dumpsites and landfill sites (92.78%), followed by incineration (4.72%) and a return to the pharmacy for proper disposal (1.38%). The remaining 1.11% flashed it down the sink (Table 6). Household respondents were asked to rank health, education, transportation, environment, and jobs, in terms of how important they are to them. More than 94% of the participants responded that their health was the most important to them. 154 out of 400 respondents ranked the environment as being of moderate importance (Table 7). Refreshingly, when they were asked if they would be ready to pay to enhance waste management services to curtail pharmaceutical contamination of rivers and streams, 273 (68.3%) responded “yes”. The majority (64.3%) of household respondents agreed with the statement that pharmaceutical residues in water affect the environment negatively (Table 8). Only 128 (32%) respondents replied “yes” when asked whether they understood pharmaceutical pollution of rivers and streams was of environmental concern (Table 8).

Table 5 Frequency of disposal of prescription and non-prescription drugs
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Table 6 Methods used by respondents to dispose of medicines (n = 360)
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Table 7 Response of participants on the importance of health, transportation, education, environment, and jobs to them (n = 400)
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Table 8 Response of participants on their willingness to better improve their environment and on the environmental effect of pharmaceutical residues
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5 Discussion

The survey revealed a gender distribution where the majority of respondents were female (56%), compared to 44% male (Fig. 2). This indicates a predominance of female respondents, which is crucial for understanding potential gender-based differences in pharmaceutical disposal practices and attitudes. In terms of age distribution, the largest group of respondents was in the 21–30 years age bracket, comprising 28% of the sample. This suggests that younger adults were the most represented group in the survey. The remaining age categories were as follows: 31–40 years (18%), 15–20 years (18%), 41–50 years (14%), 51–60 years (9%), and over 60 years (13%). The relatively high representation of individuals aged 21–30 could influence the findings, particularly regarding contemporary attitudes and practices related to pharmaceutical disposal. The distribution across other age groups provides a diverse perspective, though the lower representation in older age brackets (51–60 years and over 60 years) might limit insights into the disposal practices of these age groups.

Fig. 2
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Demographic characteristics of respondents in households: a gender, and b age of participants in the survey

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The survey conducted established that the majority (92%) of the households within the Ejisu-Juaben municipality dispose of unused and expired drugs by placing them in bins for onward disposal at dumpsites. Although the majority (86.7%) of the respondents have had some form of formal education, only a handful (1.38%) knew and used the appropriate route of disposal of unused and expired medicines. Analgesics, antibiotics, antimalarials, and other prescriptions as well as over-the-counter drugs were the frequently discarded drugs by respondents. It is therefore not surprising that most of the pharmaceuticals screened for were present in at least one sample obtained from the dumpsites within the municipality. The findings on the classes of drugs frequently disposed of in this study are similar to those of Rosal and coworkers, who found 25 compounds in the μg/L range, including acetaminophen, caffeine, and other antibiotics which exceeded the level in yearly average, and highlighted these as the widely discarded pharmaceuticals [25]. Disposal of expired and unused drugs alongside household waste has been reported in several other studies in Ghana and other parts of the world [6, 26].

Based on data from the survey, over 61% of the respondents had no idea about the acceptable route of disposal of unused and expired pharmaceutical products—returning drugs to the pharmacies or keeping them for onward disposal by the FDA. This could probably be the reason very few respondents were practicing the most appropriate means of getting rid of unused and expired medicine. This implies that if proper education on the disposal of pharmaceutical waste is rolled out, there is the possibility of an improvement in the number of people who use the proper routes. The high percentage of respondents who had no idea about the acceptable routes of disposal of unused and expired medications is similar to other studies conducted in Kumasi [15], Owabi and Barekese [2] and Sunyani [26] in Ghana. A convenient location of a drug take-back program has been suggested as a potential solution to ensure environmental protection [15]. A proper disposal system implemented could also help in the management of indiscriminate disposal of expired and unused drugs. Optimization of the prescription and dispensing practice by medical practitioners to minimize the generation of expired and unused medicines, and hence their disposal into the environment is another option [26]. Expired or unused drugs thrown into the environment have a greater propensity to trickle into nearby surface water by runoffs or even seep down the soil and eventually contaminate groundwater. The effects of this could include multi-drug resistance in the case of antibiotics and ecosystems malfunctioning by other therapeutic substances [27].

In this study, 5 out of 9 drugs analyzed were detected in the various samples. These pharmaceutical residues found in the samples collected from the dumpsites were under the umbrella of analgesics and antibiotics. Paracetamol and diclofenac were the analgesics present whilst amoxicillin, doxycycline, and metronidazole were the antibiotics. All five pharmaceuticals were present in both leachate and soil samples suggesting a far-flung occurrence of the pharmaceuticals in the dumpsites. The concentration of pharmaceuticals detected in the leachate ranged between 0.01 and 74.53 µg/L with the highest being chloramphenicol. In contrast, the levels in the soil samples ranged from (0.06–305.06) μg/kg with amoxicillin recording the highest concentration. Certain physicochemical compositions may explain these discrepancies in concentrations of chloramphenicol and amoxicillin in the two matrices. Physicochemical properties such as high solubility, acidity, and low liquid-soil sorption may have resulted in the high levels of chloramphenicol in leachate samples, whereas high liquid–solid sorption on positively charged soil may have influenced the abundance of amoxicillin in soil as suggested in the literature [2]. Interestingly, caffeine, ibuprofen, metronidazole, and ciprofloxacin were not detected at all in any of the samples collected from the dumpsites within the Ejisu-Juaben Municipality. This may be due to the rapid degradation of these analytes due to weather and other environmental factors or the inability of the analytical method used to detect these analytes at their concentrations in the environment. The concentration of pharmaceuticals recorded in this study was slightly below that recorded in other studies. This might have resulted from population differences and consumption and production patterns of these compounds. A study in Taiwan monitored the occurrence and treatment efficiency of pharmaceuticals in landfill leachates, and 19 compounds in leachate samples were reported [28]. These compounds included analgesics, antibiotics, anti-inflammatories, and other groups of pharmaceuticals. Seven of these compounds, ibuprofen, gemfibrozil, benzophenone, erythromycin, amphetamine, methamphetamine, and ephedrine, had a concentration higher than 0.1 µg/L in all four leachates. Generally, the concentration of pharmaceuticals ranged between 0.0044 µg/L and 8.1025 µg/L.

Hussain et al. studied the fate of antibiotics in the receiving environment (soil) of pharmaceutical wastewater and reported the maximum concentrations of ciprofloxacin as 3.51 µg/kg in the soil [29]. The maximum concentration of ciprofloxacin in soil from a Spanish marsh area was found to be 0.0046 µg/kg, whereas the concentrations of diclofenac and ibuprofen were below the detection limit [30]. Similarly, a study on landfills in Kumasi reported the maximum concentration of amoxicillin to be 76.62 μg/g, whereas metronidazole and penicillin were 50,080 μg/kg and 120,520 μg/kg in leachates and sediment samples [17]. The concentrations of pharmaceuticals recorded in this work varied significantly with the studies in Kumasi and other countries probably because the sampling areas were farther away from the locations of pharmaceutical units, in addition to the diversity in adsorption capacity of distinct pharmaceuticals to soil particles [31, 32]. Our study also reported metronidazole to be below the detection limit in both leachates and soil samples contrary to the Kumasi study [17]. The discrepancies in the concentration recorded in this work and others could also be attributed to lower production and rate of consumption of pharmaceuticals in Ghana contrary to Pakistan and other countries [6, 33]. It could also be that the half-lives of these compounds are relatively shorter and might have decayed faster relative to the prevailing environmental conditions in Ghana. The rate at which pharmaceuticals are completely decomposed is influenced by several factors such as weather and the nature of the waste treatment procedure. Also, the physicochemical makeup of most pharmaceuticals like acidity and high solubility in water with very low solid–liquid partition is key. These factors result in poor sorption of these compounds onto organic matter or particles [34]. The soil and leachate samples obtained from the dumpsites exhibited a pH that ranged from neutral to weakly basic (Table 2). Acidic pharmaceuticals, like the ones analyzed in this study, tend to bind to suspended solids when the conditions are basic [35]. The neutral to slightly basic pH observed in the samples ensures that the binding of these pharmaceuticals to organic matter is not significant. This, in turn, facilitates their removal and decomposition from the soil. Pharmaceuticals can have long-lasting detrimental effects on both ecosystems and human health. The concentrations of pharmaceuticals detected in water and sediment samples may result in significant environmental repercussions. A major concern highlighted by this study is the potential for ongoing, low-level exposure to antibiotics to contribute to the emergence of antibiotic-resistant bacteria. Sub-lethal concentrations of antibiotics in the environment can promote the development of resistant bacterial strains, increasing the risk of these resistance genes being transferred to other microorganisms in the ecosystem [36].

The risk assessment showed that all pharmaceutical residues detected in this study pose a high risk to the organisms studied (algae, daphnia, and fish). The predicted no-effect concentration (PNEC) for these organisms was determined using data from literature on acute toxicity. The hazard quotient (HQ) for amoxicillin and paracetamol (0.17 and 0.12) respectively, against fish in the leachates were moderate as the HQ <  < 1. In contrast, the same amoxicillin and paracetamol detected in the soil samples showed a high risk (122.02–305.06 and 30.95–1271.74) respectively, against the same organisms except for fish. On average, the HQ recorded for all pharmaceuticals in leachates against all organisms was much lower as compared to that in the soil. Chloramphenicol levels had the potential for the most impact on the organisms with the highest HQ in both leachates and soil samples. Ashfaq et al. studied and reported HQ values for paracetamol to be 64, 9.2, 5.0, and 0.11 against daphnia, S. proboscideus, D. magna, and green algae respectively, in a study on pharmaceutical residues in dumpsites in a part of Pakistan. Also, HQ values of 1,013 against fish, 253 against green algae, and 167,300 against O. latipes were recorded for ibuprofen. Ofloxacin HQ values against Vibrio fisheri, Pseudomonas putida, fish, daphnia, green algae, and Pseudokirchneriella subcapitata were found to be 4,050, 81,000, 153, 56, 4,050, and 7,364, respectively. Ciprofloxacin showed a risk quotient of 220 and 440 against green algae and M. aeruginosa, respectively, but exhibited low risk against fish and daphnia with HQ <  <  < 1. Moxifloxacin also showed a low risk against fish, daphnia, and green algae implying that moxifloxacin has no adverse impact on these species in the receiving environment [6]. Similarly, Gyesi et al. reported an HQ range (0.15–7440.69) for fish, daphnia, and algae in water and sediment from Barekese and Owabi reservoirs. The least HQ reported was for paracetamol against fish and the worst was diclofenac against algae in water [2]. In light of the HQs recorded in this study, a great level of damage could be caused to the terrestrial ecosystem.

The presence of pharmaceutical residues, especially antibiotics, in the environment, can have several potential effects on plant life in the ecosystem. Some pharmaceuticals are known to be phytotoxic. At high concentrations, these pharmaceuticals may interfere with various physiological processes, such as nutrient uptake, photosynthesis, and root development, leading to reduced growth, wilting, leaf discoloration, or even plant death. Again, pharmaceuticals can alter microbial communities by disrupting the natural balance of microbial communities in soil. Some of these microbes play crucial roles in nutrient cycling and plant–microbe interactions. Thus, changes in microbial diversity and composition can impact plant health and growth. Due to their ability to promote drug resistance, the presence of pharmaceuticals in the environment could potentially affect the plant-associated microbiota and increase the risk of antibiotic-resistant pathogens in the ecosystem. Plants often form beneficial symbiotic associations with microorganisms, such as mycorrhizal fungi and nitrogen-fixing bacteria. Pharmaceuticals may disrupt these symbiotic relationships, impairing nutrient acquisition and affecting plant health and productivity. It is important to note that the specific effects of pharmaceuticals on the environment depend on factors such as the type of pharmaceutical, its concentration, exposure duration, and the characteristics of the plant species and ecosystem [37, 38]. It is therefore imperative that policies that promote safe and proper disposal of used and unused pharmaceuticals are adopted and implemented to protect organisms in the ecosystem, maintain ecosystem health, and attenuate potential cascading effects on humans.

6 Conclusion

This study showed that the majority of the household participants in the survey within the Ejisu-Juaben municipal assembly employ inappropriate methods for the disposal of expired and unused pharmaceuticals. More than 83% of the respondents asserted that they dispose of these environmental contaminants in waste bins as part of domestic solid wastes for onward disposal at dumpsites. Over 80% of respondents had little knowledge about the bearing of these unapproved routes of disposing of pharmaceutical wastes on human health, the environment, and the ecosystem at large. High levels of the pharmaceuticals were detected in all the environmental matrices (74.53 µg/L and 305.06 in leachate and soil, respectively). The HQ values (far greater than 1 for both soil and leachate samples), were very high for most of the pharmaceutical residues against the three species studied, especially all detected pharmaceuticals in the soils as well as diclofenac in the leachates. These values indicate damaging risks to the studied organisms. This is the first time a study of this nature has been carried out in the Ejisu-Juaben municipality. People in other regions of Ghana may be engaging in similar unacceptable disposal methods for unused and expired medicines, with little or no knowledge of the dangers they pose to the environment. There is an obvious need for a larger-scale survey while developing strategies to improve the disposal of unused and expired pharmaceuticals. Routine monitoring of environmental levels of pharmaceutical residues is required to maintain the ecosystem’s health. Remediation strategies must be developed and implemented to forestall further environmental degradation vis-a-vis an education campaign on the proper methods of disposal of pharmaceutical waste.