Does the application of biosolids pose a health risk?

Good hygiene practices are essential for persons coming in contact with biosolids. As in many other fertilisers and soil amendments, human sickness may result from exposure to chemicals, toxins or pathogenic organisms. Biosolids may contain some or all of these at various stages, particularly at the time of production. However, there are many barriers available to protect us from these.

The potential health concerns for users of biosolids are excessive levels of toxic metals or chemicals, or presence of potentially pathogenic micro-organisms (e.g.: viruses and bacteria).

All producers of biosolids are required to monitor their product for contaminants. Guidelines published by State, Territory and national governments in Australia and New Zealand ensure that good practice is followed when Biosolids are applied to agricultural land. In these circumstances, there is no danger to health from the resulting crop.

The wet material may provide a suitable environment for organisms, and care is required to ensure the health of workers during transportation and application of moist material. After application to farmland, the biosolids decompose quickly into the soil (exposure to sunlight and drying causing rapid die-off of any remaining pathogens) and naturally occurring bacteria become dominant.

Only the highest quality material is able to be used in circumstances such as composting or application to leaf crops. Generally, biosolids are applied to broadacre and grain crops where the time between application, sowing of seeds and harvesting of mature crops can be from three to six months. In the case of grain crops, the crop itself will be subject to further refinement to produce flour and other products.

As is the case with many other foods or products used in conjunction with food production, there are ongoing concerns about various chemicals: that they may be present in very tiny concentrations, or their effects have not yet been identified. It is important to note there have been no identified cases of death or illness from exposure to biosolids that have been used appropriately, in line with relevant Guidelines.

Protecting human health is a cornerstone of the various Biosolids Guidelines in place in Australia and New Zealand. These Guidelines are usually endorsed by relevant Departments of Health or related regulatory authorities. Biosolids applied in accordance with Guidelines to grow crops or graze stock for human consumption presents a negligible risk to the consumer.

A summary of the specific Guidelines for biosolids management in Australia and New Zealand can be found here.