Drugs and personal care products as ubiquitous pollutants: occurrence and distribution of clofibric acid, caffeine and DEET in the North Sea

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Abstract

An analytical method is presented, which allows the simultaneous extraction of neutral and acidic compounds from 20-L seawater samples at ambient pH (∼8.3). It is based on a solid-phase extraction by means of a polystyrene–divinylbenzene sorbent and gas chromatographic-mass spectrometric detection, and provides detection limits in the lower pg/L range. The method was applied to the screening of samples from different North Sea areas for clofibric acid, diclofenac, ibuprofen, ketoprofen, propyphenazone, caffeine and N,N-diethyl-3-toluamide (DEET). Whereas clofibric acid, caffeine and DEET showed to be present throughout the North Sea in concentrations of up to 1.3, 16 and 1.1 ng/L, respectively, propyphenazone could only be detected after further clean-up. Diclofenac and ibuprofen were found in the estuary of the river Elbe (6.2 and 0.6 ng/L, respectively) but in none of the marine samples. Ketoprofen was below the detection limit in all samples.

Introduction

An ubiquitous prevalence in the marine environment has been verified for several classical persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs), hexachlorocyclohexanes (HCHs) and DDT. These are characterised by their lipophilicity, low degradability, and thus high bioaccumulation factors. At present, increasing attention is being paid to polar, often less persistent compounds, some of which, namely pharmaceuticals and personal care products, may act as if they were persistent because of their continuous input and permanent presence in aquatic systems (Daughton and Ternes, 1999). As a consequence, some compounds of this origin are being found throughout limnic systems, in ground and in tap water which may suggest their ubiquitous distribution. However, knowledge on their presence in the marine ecosystem is very limited. Their detection in the open sea would confirm their ubiquitous character and could lead to new insights into their persistence. In this work, emphasis is placed upon the following polar xenobiotics:

Pharmaceuticals: According to their usage in human or veterinary medicine pharmaceuticals and their metabolites, respectively, sooner or later reach aquatic systems. Input may take place directly (e.g., from aquaculture), via effluents of sewage treatment plants after ingestion and excretion, or by leaching from soil treated with drug residue containing manure (Halling-Sørensen et al., 1998). Release from production to surface waters has been reported as well, e.g., for carbamazepine (Schullerer et al., 1997). The permanent exposure of aquatic organisms to pharmaceuticals is necessarily a matter of concern since pharmaceuticals are designed to be biologically active, and they are thus likely to affect non-target organisms as well. Furthermore, evidence was presented for the development of antibiotic-resistant bacteria upon exposure to untreated hospital and domestic sewage effluents (Andersen and Sandaa, 1994), for genotoxic effects of certain drugs (Hartmann et al., 1998), and for endocrine disruption by therapeutically administered synthetic and natural hormones (Purdom et al., 1994).

Several studies have shown the widespread occurrence of pharmaceutical compounds in the environment, thus establishing these compounds as a new class of priority pollutants (Stan et al., 1994, Ternes, 1998, Buser et al., 1998a). The most frequently detected substances comprise clofibric acid, ibuprofen and diclofenac, while propyphenazone is prevalent in the Havel/Elbe river system (Heberer et al., 1998, Franke et al., 1995). However, very little is known about the presence of drug residues in marine ecosystems. Buser et al. (1998b) reported the occurrence of clofibric acid in the North Sea at concentrations of approximately 1 ng/L, while ibuprofen was not detected above the detection limit of 0.2 ng/L (Buser et al., 1999).

Caffeine: Caffeine is consumed in large amounts in many countries in the form of beverages and, to a minor extent, as analeptic and in combination with analgesics to enhance their effect. Consequently, caffeine was detected in most non-target screening studies (STP effluent, Paxéus, 1996; river water, Franke et al., 1995, Hendriks et al., 1994, Richardson and Bowron, 1985; seawater, Weigel et al., 2001). Systematic research on the distribution of caffeine in the aquatic environment started only recently and revealed its presence in surface and ground water in the ng/L to μg/L range (Prösch and Puchert, 1998, Burkhardt et al., 1999, Seiler et al., 1999). All three studies propose the use of caffeine as a tracer of domestic sewage. The ecotoxicological relevance of the relatively high concentrations in the environment has not been investigated yet. Kiefer and Wiebel (1998) observed an enhancement of the genotoxicity of certain chemical carcinogens by caffeine.

DEET: DEET is widely used as an insect repellent for humans. It has also been applied in agriculture, e.g., to grazing cattle (Riha et al., 1991). DEET enters the aquatic environment mainly via communal sewage treatment plant (STP) effluents and only to a diminishing extent via atmospheric deposition (Knepper et al., 1996). Similar to caffeine, it was detected in many non-target screenings (river water, Franke et al., 1995, Hendriks et al., 1994; seawater, Weigel et al., 2001).

Information on the occurrence and distribution of contaminants in marine ecosystems is important mainly for two reasons: (i) their presence in the sea indicates that they are sufficiently persistent to withstand transformation on their way to and within the sea, where no new inputs occur (apart from atmospheric deposition, which is not to be expected in case of the mostly polar or even ionic pharmaceuticals); (ii) physico-chemical and biological conditions in marine aquatic systems are significantly different from limnic ones, e.g., salinity, pH, temperature, concentrations of organic compounds, and biological activity. This may lead to a completely different behaviour of organic chemicals like, in some cases, an enhancement of stability.

In a previous work, water sample extracts from the North Sea were screened for the presence of organic xenobiotics (Weigel et al., 2001). Among other substances, we identified the pharmaceutical compounds carbamazepine and propyphenazone, as well as caffeine and DEET. In this work, we evaluated the applicability of the analytical procedure, which was originally designed for non-target screening, to the target analysis of clofibric acid, diclofenac, ibuprofen, ketoprofen, propyphenazone, caffeine and DEET. Thereafter, 20-L water extracts from selected parts of the North Sea were analysed with regard to these target compounds, in order to gain a more comprehensive survey on their distribution in the aquatic marine environment.

Section snippets

Chemicals and materials

Glass fibre filter candles (exclusion size=0.5 μm) were obtained from Voigt (Wernau, Germany). Prior to application they were cleaned by heating them for 72 h at 693 K (420 °C) followed by duplicate Soxhlet extraction (200 mL n-hexane/ethyl ethanoate (ethyl acetate), 6 h). Glass fibre filter disks GF/C (diameter=47 mm, exclusion size=1.2 μm) were supplied by Whatman (Maidstone, UK). The sorbent Bakerbond SDB-1 (styrene–divinylbenzene co-polymer, particle size=40–120 μm, pore size=27 nm, surface

Methodological parameters

Recovery as determined by replicate (n=4) extractions of 20-L samples spiked at the 5-ng/L level was in the range of 70% for the neutral analytes and of 40% for the acidic ones. Linearity of the method was given over the complete concentration range investigated herein (0.05–50 ng/L) with correlation coefficients r2 (linear regression) of 0.9996 or above. The linearity is illustrated for DEET in Fig. 1. The LOQs were in the lower pg/L range for most acidic analytes (2–33 pg/L), and

Methodological aspects

The outstanding feature of the present method is its ability to extract neutral and acidic analytes from water samples at basic pH simultaneously. This is especially valuable for seawater analyses because due to its high buffering capacity the neutralisation or acidification to a pH of 2, as often proposed for the extraction of acidic analytes, would require the addition of large amounts of hydrochloric or sulfuric acid. By contrast, the present method simplifies sample handling, allows on-line

Conclusions

The method presented in this work fulfils the requirements of marine analytical chemistry; very low limits of quantification are reached, and the simultaneous extraction of neutral and acidic analytes is possible without prior acidification of the sample. The application of the method to North Sea water samples established the pharmaceutical drug metabolite clofibric acid, the widely used psychoanaleptic caffeine, and the insect repellent DEET as ubiquitous pollutants in this aquatic ecosystem.

Acknowledgements

We are grateful to N. Theobald (BSH, Germany) for enabling the participation in the RV Gauss cruises, as well as E. Hammermeister and S. Biselli (BSH, Germany) for supplying the basic maps. Thanks are also due to F. Hoffmann for his assistance with the graphics.

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