Pharmaceutical Residues in Drinking Water

Pharmaceuticals are indispensible to human as well as to animal health. Yet their ecological impact gives cause for concern. Many pharmaceuticals are persistent, which means they are degraded only slowly and accumulate in the environment. In higher concentrations these residues may be toxic for aquatic organisms. Since 1974 the German Environmental Agency (UBA) has been compiling an environmental research database (UFORDAT) which comprises monitoring data on pharmaceutical residues in the environment. Similarly, regional water suppliers regularly have their drinking water tested for pharmaceutical residues and publish the data.

Detection of pharmaceuticals in drinking water by the ifp residues Lab

We test for pharmaceutical residues in water by means of HPLC-MS/MS. The range of substances comprises the most frequently used human and veterinary pharmaceuticals, including their relevant metabolites:

  • Analgetics and antiphlogistics, e.g. Diclofenac, Ibuprofen
  • Antibiotics, e.g. Chloramphenicol, Sulfamethoxazol
  • Anticonvulsants, e.g. Phenobarbital, Primidon
  • Antilipidemics, e.g. Bezafibrat, Fenofibrat
  • Beta blockers, e.g. Metoprolol, Propranolol
  • Gestagens, e.g. Norethisteron
  • Contrast agents, e.g. Amidotrizoesäure, Gadolinium (by means of ICP-MS)
  • Psychoactive drugs, e.g. Diazepam, Oxazepam
  • Cytostatics, e.g. Cyclophosphamid
  • Veterinary pharmaceuticals, e.g. Sulfamethoxin, Tiamulin (antibiotics), Ivermectin (antiparasitics)

Human pharmaceuticals get into the water via faeces and incorrect disposal

Human pharmaceuticals and their metabolites get into the municipal wastewater mainly via human excretion. A further source not to be underestimated is incorrect disposal of pharmaceuticals, e.g. in the toilet or domestic waste that is not burnt. Since the technologies used in municipal sewage plants do not suffice to entirely remove pharmaceutical residues, these substances enter flowing waters and the drinking water together with the cleaned water. Pharmaceuticals are highly mobile thanks to their mostly polar structure. This allows them to get into the groundwater through leaks in the wastewater system or as a result of surface water seepage.

Veterinary pharmaceuticals in groundwater: the result of intensive agriculture

Veterinary drug residues result from the intensive use of medication in industrial livestock farming as found in conventional agriculture. The substances and metabolites that are then excreted by the animals get into farm fertilizer which is used to treat the soil and arable land. From there the substances seep into the soil and into the groundwater. Surface waters may also be polluted by surface runoff after heavy rainfalls.

Risk assessment of pharmaceutical residues in drinking water

In Germany, risk assessment of pharmaceutical residues in drinking water is done by the Federal Environmental Agency (UBA) based on toxicological data. For non-genotoxic compounds, the Agency recommends a general target value (precautionary value) of max. 0.1 µg/L per individual substance in order to minimize consumer risk. Up to this concentration health assessment is not necessary, since no risk is expected for any of the age groups including infants and toddlers. The Federal Environmental Agency specifies health orientation values, guideline values and intervention values, which are used to evaluate the health risk of pharmaceutical residues in drinking water. If these health orientation values and the guideline values are not exceeded, the drinking water is declared safe for human consumption. If intervention values are reached or even exceeded, the drinking water is no longer classified as safe for consumption. In this case the origin of pharmaceutical entry should be investigated and its concentration minimized as far as possible.

Chlorate and Perchlorate Residues in Drinking Water

The detection of compounds containing chlorine in water is leading to increasing discussions. Perchlorate has been detected in groundwater since the 1950s. According to newer studies, chlorate in drinking water seems to originate from water processing methods that involve the use of various chlorination agents.

At ifp chlorate and perchlorate are detected by means of the QuPPe method (Quick Polar Pesticides Method) and by means of LC-MS/MS.

CVUA Stuttgart tests for chlorate in drinking water

In December 2014 CVUA Stuttgart (Chemical and Veterinary Investigation Office) had found significant concentrations of chlorate in drinking water. The German government agency had analysed a total of 109 drinking water samples for chlorate (half of them a cross-section of drinking water from various origins, half of them risk-based). Two thirds of the samples showed chlorate levels above 0.01 mg/L. In 16% of the samples the concentration was above 0.05 mg/L, almost 5 percent even exceeded 0.1 mg/L.

These findings substantiate the arguments of the food industry that chlorate is found on fruit and vegetables due to the fact that it is washed with drinking water containing chlorine. The results showed that especially water from community-owned supplies or water supply associations frequently contains chlorine, since here higher concentrations of chlorine are added for hygienic reasons. Water from long-distance supplies, by contrast, rarely contains chlorine.

CVUA Stuttgart also found that different chlorination agents used in water treatment have different effects on the drinking water’s chlorine concentration. While chlorate concentrations of more than 0.05 mg/L are more often found when using chlorine dioxide or chlorine bleaching, this concentration is significantly less often exceeded when using chlorine gas in water treatment.

Risk assessment of chlorate residues in drinking water

So far there is no statutory limit value for chlorate in drinking water, but the World Health Organisation (WHO) has issued a preliminary guideline value of 0.7 mg/L. The ADI (allowed daily intake) of 0.01 mg per kg of body weight deduced from toxicological data by the WHO was so far also recommended as a basis for risk assessment by the German Federal Institute for Risk Assessment (BfR).

In June 2015 the European Food Safety Authority (EFSA) published a scientific report in which it deduces toxicological maximum concentrations for chlorate and evaluates the suitability of the WHO guideline value of 0.7 mg/L. With regard to chronic risk, the EFSA deduced a maximum tolerable daily intake (TDI) of 0.003 mg/kg body weight (bw) and day (d), with regard to acute risk, the Authority deduced an acute reference dose (ARfD) of 0.036 mg/kg bw. This implies that the WHO guideline value for drinking water (0.7 mg/L) is not sufficient to guarantee the safety of the population in the EU. According to the EU Commission and the German Ministry of Food and Agriculture (BMEL) the results of this expert report are now to be analysed in depth. Possibly an EU-wide limit value (probably < 0.7 mg/L) for drinking water will be defined that will also serve as a guideline value for maximum concentrations in food.

Risk assessment of perchlorate residues in drinking water

Increased perchlorate concentrations in water may be the result of natural occurrences in the rock and soil. However, there is reason for growing concern due to the comparatively low toxicologically relevant concentrations. Oral intake of water or food containing perchlorate represents the primary path of human exposure to perchlorate. In October 2014 the EFSA defined a tolerable daily intake quantity (TDI) of 0.3 μg/kg body weight and day. This would mean that a person weighing 75 kg who drinks 2 litres of water a day would consume 11 µg/L of perchlorate each day.