What is the fine-grained topic of the following text: Earlier this month, New York Times' Matt Flegenheimer wrote about how, in the last five years, the City of New York has spent more than $18 million just to deal with the immense amount of wet wipes clogging up the city’s wastewater treatment plants. Only return the topic.
New York City's expenditure on dealing with wet wipes clogging wastewater treatment plants.