The impact of triclosan, an antibacterial agent commonly added to consumer products, on microbial populations in soil irrigated with waste water from households was examined. It was found that irrigation of soil with triclosan containing waste water results in both an increase in resistant bacteria and a concomitant decrease in overall microbial community diversity. These changes in the soil microbiota raise public health and environmental concerns about the release of untreated household waste streams into terrestrial ecosystems. Before irrigation with waste water can become a useful water reuse alternative, additional research focusing on the long-term impacts of triclosan and other pharmaceuticals and personal care products is needed.



18. The passage provides information on each of the following except

A) whether soil irrigation with triclosan-containing waste water affects how many different types of bacteria will be found in that soil
A decrease in community diversity in the soil means there will be less types of microbes found in any soil irrigated with triclosan containing waste water. Bacteria are both microbes and members of the microbial community. So how many types? Not many types.

B) the origin of the triclosan detected in the soil samples studied.
It was from consumer products used in households.

C) whether irrigation with waste water is a viable idea
see Official Explanation

D) what changes soil microbiota undergo when exposed to triclosan
There will be an increase in triclosan-resistant bacteria and a decrease in diversity within the soil microbiome

E) the reasoning for introducing waste water into the ecosystem studied
To resuse it for the purpose of irrigation