The Bermuda-registered exchange did not provide a reason for the delistings, but all three are privacy coins—a class of cryptocurrencies that offer untraceable transactions. Monero is private by default, and ZCash and Dash have an option for private transactions.
Privacy coins are under scrutiny by regulators, who consider them facilitators of illegal activity. Darknet market White House Market, for instance, only accepts Monero transactions because of its privacy features; it's easier to trace Bitcoin transactions.
Bittrex cites "evolving regulatory standards and other compliance issues" among its reasons for delisting tokens.
Earlier this week, Bittrex was one of several exchanges to delist XRP after the US Securities and Exchange Commission filed a lawsuit against XRP's creators for raising $1.3 billion in ongoing unregistered securities sales. Ripple, the company named in the lawsuits, denies the allegations.
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