Study and determination of some selected herbicides and their metabolites in sewage sludge: Health risk through the application to agricultural lands
Sewage sludge and agriculture
Sewage sludge is widely used as a fertilizer or soil conditioner in agriculture lands for a few decades. It is considered a beneficial by-product of the wastewater treatment process due to its rich content of nutrients such as nitrogen and phosphorus, and organic matter that are crucial for soil productivity [1]. Similarly, land application of sewage sludge has been practiced for decades in forests, mine reclamation sites, and other drastically disturbed lands such as parks, and golf courses [1], [2]. The use of sewage sludge reduces the need for commercial fertilizers, thereby reducing the impacts of high levels of excess nutrients entering the environment [2]. The production of sewage sludge from wastewater treatment plants is growing in European Union member states and it is estimated that, just about 35 % sludge produced in the region spread directly for agricultural purposes and about 12 % is used for composting and application for the soil in forestry, gardens, and city greens [3]. Similarly, more than half of sludge production is composted or applied to agricultural lands in some countries such as the Czech Republic, Lithuania, Ireland, and Hungary [4]–[6].
Is applying sewage sludge to agricultural land harmful to human health?
The production of sewage sludge from wastewater treatment plants is growing in European Union member states and it is estimated that, just about 35 % sludge produced in the region spread directly for agricultural purposes [3]. However, in recent decades the sustainable use of sewage sludge on agricultural lands became an environmental and health issue. Sewage sludge may contain numerous contaminants such as heavy metals, pathogens, and different organic pollutants coming from domestic and industrial wastes, agricultural runoffs, and atmospheric deposition [7]. Hence, persistent contaminants coming through sewage sludge may enter the food web through bioaccumulation and pose a risk to human health [1].
How herbicides and their metabolites in sewage sludge effect to human health?
Herbicides are the most used pesticide throughout the world accounting the 52 % of the total pesticide market [8]. Due to their excessive use, the concern about potential environmental hazards increased in recent years [9]. They are considered persistent organic pollutants (POPs) which, create a wide range of toxic effects that pose a potential hazard to the environment [10]. The wide applications of herbicides in both agriculture and non-agriculture sectors such as the home and garden, industries, lawns, parks, and golf courses create contamination of both urban and rural areas [11]. Active substances of herbicide can produce more toxic metabolites than active ingredients through the environmental process such as microbial degradation. Herbicides and other organic pollutants that enter wastewater may volatilize, disintegrate into more or less harmful chemicals than they were originally, sorb into sludge, or be released into the aqueous effluent through biotic and/or abiotic processes [12]. Many herbicides degrade to relatively stable and persistent compounds, and some of these degradates are as toxic, or even more toxic than their parent compounds [10]. These compounds can enter to food web and ultimately affect human health adversely. Numerous studies investigated the occurrences of herbicides in environmental samples and their effects on human health and the environment [13]. Nevertheless, very few research looked into the herbicides and their metabolites in sewage sludge. The use of sewage sludge for agricultural uses and the development of standards or guidelines with maximum contamination levels depend on the knowledge of herbicides and their metabolites in the sludge.
References
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[2] USEPA, “Biosolids Generation, Use, and Disposal. ,” 1999.
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[6] Eurostat, “Environment and energy, environment, water, water statistics on national level, sewage sludge production and disposal.”
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[10] D. W. Kolpin, D. J. Schnoebelen, and E. M. Thurman, “Degradates Provide Insight to Spatial and Temporal Trends of Herbicides in Ground Water,” Ground Water, vol. 42, no. 4, pp. 601–608, Jul. 2004, doi: 10.1111/j.1745–6584.2004.tb02628.x.
[11] J. , C. J. , D. H. Shepard, “Forestry herbicides in the United States: an overview,” Wildl Soc Bull, vol. 32, no. 4, pp. 1020–1027, 2004.
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