Spreading of Bio-wastes onto Soil Surfaces to Control Pathogens: Human Health and Environmental Consequences

Abstract

Thousands of tons of animal and human wastes are produced every day across the globe. Their continuous use as fertilizers or soil amendments on agricultural lands has raised severe health and environmental concerns. Incorporating bio-wastes into the soil is one of the best management strategies to control the run-off of nutrients from the soil surface and, in turn, protect freshwater. However, exposing bio-waste to sunlight in the field is considered to be one of the most cost-effective methods to control pathogens. Considering the differences among different bio-waste management strategies, there is a need for a review of the current knowledge on the practice of spreading bio-wastes onto the soil surface. Specifically, this information would help us to better understand the fate of pathogens upon their exposure to the open environment, how the presence of bio-waste on the soil surface can threaten humans and the environment, and the costs and benefits of surface-applied bio-wastes. Current review of the literature revealed a lack of understanding of the factors responsible for killing pathogens on the soil surface. More than 150 pathogens (including different viruses, bacteria, protozoan and helminth) have been reported to be present in different bio-wastes, but the majority of studies have focused on a few common pathogens. Similarly, over the last decade, each year at least 1 new pathogen is being reported which can threat public health but there is a paucity of knowledge concerning the fate of pathogens under field conditions. Similarly, the techniques used for the detection of pathogens were found to be variable and inconclusive, making it difficult to compare the results of different studies. Therefore, given that the tools for the evaluation of pathogens have serious limitations and the survival characteristics of many (old and emerging) pathogens are yet to be discovered, the spreading of bio-wastes (treated or untreated) onto the soil surface (i.e., unincorporated) may not only further increase the threat for human health but also further aggravate the environment.