11
Apr
Soils in Urban and Natural Lands Equally Contaminated, Study Finds
(Beyond Pesticides, April 11, 2023) Natural areas are often considered more pristine than urbanized locations, but a new study published in Nature Communications shows that the soils in natural lands can be just as polluted as those in more densely populated cities. The findings underscore the broad impacts that human activity is having on the health and stability of natural systems around the globe. In order to address widespread contamination, advocates urge government regulators to consider the full cradle to grave life cycle of toxic materials before releasing them into the environment.
An international contingent of scientists came together to conduct this research on a global scale, looking at soils on every continent. Soil samples were collected from urban greenspaces and nearby natural areas and paired together. Sampling was conducted in 56 cities in 17 countries, representing six continents. These data were also compared to soil samples taken from remote ecosystems in Antarctica. Scientists tested soils for eight heavy metals, 46 pesticide residues, microplastics, and antibiotic resistance genes.
Results reveal a wide distribution of tested contaminants in all samples taken. “Although the level of individual contaminants varied greatly across locations, we detected significant correlations among each type of soil contaminants studied,” the article explains.
For metals, urban greenspaces had slightly higher levels than natural areas, a variation scientists attribute to anthropogenic factors. For instance, in 42% of urban sites and 36% of natural areas, arsenic contamination exceeds soil contamination levels set under regulations by the Finnish government.
Pesticides were widely detected, including in 63% of natural areas tested. Surprisingly, there was no significant difference between these detections and those found in urban greenspaces. However, researchers indicate these data are likely an underestimate, as per the study’s supporting information, they did not measure some of the most widely used pesticides like glyphosate, 2,4-D, and paraquat. Scientists reason that atmospheric transport is likely playing a role, as well as potential deposition from agricultural sites (farm soils were not tested in the study).
Similar to other results, microplastics were widespread in every soil tested. This was also reasoned a result of atmospheric transport, with small fibers from plastic-based fabrics, ropes, nets, and other materials the likely source.
Antibiotic resistance genes were ubiquitous in both natural and urban soils, though the type of genes varied by soil. Urban greenspaces contained more diversity of these genes than natural areas. But the close similarity to the contamination is likely a result of physical movement of bacterial cells from urban to natural areas.
Despite its remote location, Antarctic soils did exhibit some of these major contaminants. In particular, microplastics were found to be just as widespread in Antarctic soils as those in all other locations. Pesticides were detected, but with less frequency, while levels of heavy metals fell below regulatory concern, and antibiotic resistance genes were below the level of detection.
Looking deeper into the findings, researchers determined that population density is the largest factor associated with the presence of microplastics. The less wealthy a city is, the more likely there would be microplastic and heavy metal contamination. For pesticides and antibiotic resistance genes, soil fertilizer applications is the greatest factor, indicating a significant human role in the global spread of these hazards. “Together, our work demonstrates that soils in nearby natural areas are as contaminated as our urban greenspaces at a large-spatial scale,” the authors write.
This is not the first study to find toxic contaminants in areas traditionally considered pristine or untouched. A 2020 study found that arctic glaciers are trapping pesticides and other atmospheric pollutants, and subsequently releasing them as they melt.
The release of any toxic material can have long term effects that are not limited merely to the location where such material was applied. Pesticides and other hazardous substances drift from direct application, volatilize, or become stirred up by dust, and can be taken into the atmosphere and deposited in locations hundreds of miles away.
Beyond Pesticides has long fought for a precautionary approach to the regulation of toxic pesticides and other materials. In order to safeguard health and the environment now and for future generations, it is critical pass laws that consider the full life-cycle of a material, and forgo production if hazards are too high. Take action today by telling the U.S. Environmental Protection Agency and Congress that all impacts from toxic pesticides- cradle to grave- must be considered before allowing use.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Nature Communications
Image Source: Wikimedia Commons
