Research project NFR-141009

Project abstract

In recent years, moulds have been paid increased attention as agents of human health problems, and studies have indicated water as a possible source of moulds. Little is known about the presence of moulds in Norwegian drinking water, and increased knowledge is required. The aim of the present study was to determine the occurrence and distribution of mould species in a selection of Norwegian drinking water distribution systems, and finally to consider their potential impact on human health and water quality.

The present study demonstrated that water from all parts of the investigated Norwegian water distribution systems regularly contains moulds. The distribution systems may serve as a dissemination route for a wide diversity of mould species to private homes and hospitals. A total of 106 different mould species were recovered from Norwegian water. When moulds are recovered from water, species of the dominating genera Trichoderma, Penicillium or Aspergillus are often present in the samples. The surface-sourced water is tree times more likely to contain moulds than underground-sourced water. Moulds are also more likely to be recovered from cold water and showers than from hot water, although some thermotolerant species may be established in hot water facilities. The distribution of moulds throughout the water systems indicates that several mould species not merely are passive contaminants but may also have the ability to be established in the water system. The water distribution systems have high potential for biofouling, and mould growth in biofilms on pipe surfaces or in water installations are probably an important source of mould contamination of water. The current water treatment is not sufficiently effective in removing moulds or spore forming Bacillus spp. from raw water. The frequency of moulds and Bacillus at the different sampling points seems to follow the same trend. This may indicate a common source of contamination, and suggests that moulds and Bacillus might reside in the same biofilms. Soil may be a possible source of both moulds and Bacillus, and the microorganisms may enter the distribution system either via soil erosion into the water source, or by leakages of soil and water through damaged water pipes. Alternatively, contact with air may also contribute to mould contamination of the water. Moulds may have a diverse impact on humans, and may potentially be pathogenic, allergenic and toxigenic. Some species may also cause undesirable sensoric changes in drinking water, such as foul taste and odour. Mould contaminated water could also be a possible source for spoilage of food and beverage. The link between waterborne moulds and human health is still not fully understood, but it is important to be aware that species of clinical concern in debilitated or immunosuppressed individuals are also present in drinking water. Moulds may be aerosolized in indoor air when water passes installations such as taps or showers, and may thus be inhaled. Elevated levels of certain mould species may therefore constitute a potential health risk in susceptible groups. For all these reasons, the mycobiota of water should be considered when microbiological safety and quality of drinking water are assessed. It seems clear that moulds should be included in the Norwegian water supply and drinking water regulations, and further research to establish accurate parameters should be performed.

Principal objective and sub goals

Principal objective:

• Study the occurrence and significance of moulds in drinking water, with emphasis on human health and water quality

Sub-goals:

• Obtain increased knowledge about the occurrence and distribution of moulds in Norwegian drinking water
• Compare surface water and ground water, in addition to other potential factors influencing the occurrence of moulds in water
• Study the correlation between moulds and other microorganisms in drinking water
• Evaluate the significance of moulds in water for human health
• Obtain increased knowledge in order to propose guidelines for the occurrence of moulds in water

Project leader

• Dr. Ida Skaar, Section of Mycology, Department of Feed and Food Hygiene

Internal project partners at the National Veterinary Institute:

• Gunhild Hageskal, PhD-student, Section of Mycology, Department of Feed and Food Hygiene

External national project partners:

• Norwegian School of Veterinary Science (NVH), Oslo, Norway
• Rikshospitalet University Hospital, Oslo, Norway
• University of Oslo (UIO), Norway

External international project partners:

• Professor Sybren de Hoog, Centraalbureau voor Schimmelcultures (CBS), Utrecht, The Netherlands

Funding sources

• The Norwegian Research Council (NRC), grant number 141009
• The National Veterinary Institute, Norway

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