Sen. Maggie Hassan (D-N.H.) sent an open letter to the Entertainment Software Rating Board (ESRB) today urging the industry's self-regulatory body to "review the completeness of the board's ratings process and policies as they relate to loot boxes and to take into account the potential harm these types of micro-transactions may have on children."

Loot boxes—which offer randomized in-game rewards, often in exchange for real money—concern Hassan for the "psychological principles and enticing mechanics that closely mirror those often found in casinos and games of chance," as the letter reads. While acknowledging "robust debate over whether loot boxes should be considered gambling," Hassan argues that "they are both expensive habits and use similar psychological principles" and thus deserve extra scrutiny. "The potential harm is real."

Hassan urged the ESRB in the letter to examine whether loot boxes are being marketed "in an ethical and transparent way that adequately protects the developing minds of young children from predatory practices." She also asked the board to "collect and publish data" on how developers and players use loot boxes.

So far, Hassan has stopped short of urging any government intervention on the loot box issue or even specific industry moves to self-regulate their use. But alongside the letter, Hassan offered some pointed questions to nominees for the Federal Trade Commission at a Commerce Committee hearing today. When asked whether games that "allow in-game purchases for surprise winnings" deserved attention from the FTC, all four nominees agreed that it was something worth looking into.

Hassan, who said she heard about loot boxes from a constituent, took time during the hearing to highlight the FTC's previous finding that the ESRB is "one of the most effective voluntary enforcement boards" in entertainment. "That is why I am confident that the ESRB will take this seriously... We should be doing all we can to protect our children and to inform parents about their options when it comes to these types of games."

In recent months, state legislators in Hawaii Washington , and Indiana have introduced legislation intended to regulate or restrict the availability of loot boxes in games, especially for minors. But Hassan's letter is the first public attention the issue has received from the federal government.

The ESRB did not immediately respond to a request for comment from Ars. The organization has previously said in a statement that "while there's an element of chance in these mechanics, the player is always guaranteed to receive in-game content (even if the player unfortunately receives something they don't want)."

[Update: The ESRB sent Ars the following statement: "We received Senator Hassan’s letter and appreciate her confidence in and support of the ESRB rating system. For more than two decades we have earned the trust of parents around the country by helping them make informed decisions about the games their children play. As the industry evolves, so does our rating system, and we will continue to make enhancements to ensure parents continue to be well-informed. We will also continue to provide information about additional tools, including parental control guides, that help parents set spending and time limits and block potentially inappropriate games based on the ESRB-assigned age rating."]

The Entertainment Software Association, an industry trade group, was also not immediately available to comment. The group has said in previous statements that it considers loot boxes to be "a voluntary feature" that lets "the gamer make the decision" to "enhance their in-game experience."

Hassan's interest in loot boxes echoes somewhat the interest former Senator Joseph Lieberman and others showed in video game violence in the early '90s. That Senatorial interest led to congressional hearings over games such as Mortal Kombat, which in turn led to the creation of the ESRB in 1994.

Further Reading Clinton, Lieberman push for Federal game ratings oversight

More than a decade later, Lieberman and Sen. Hillary Clinton sought federal oversight over the industry rating board via the Family Entertainment Protection Act . That bill never became law, and similar laws in many states were overturned by a 2011 Supreme Court decision