"alert them about" is correct and usable in written English.
You can use it when you want to draw attention to a specific topic or issue that you want someone to be aware of. For example: "I think we should alert them about the upcoming changes to the company's policies."
The Quaids say nobody called them to alert them about the mistake.
The police said that several people tried to alert them about the driver of the pickup truck, identified as Michael R. Gagnon, 24, of Adrian, Mich.
The North Face plans to eventually send branded texts when people arrive at a hiking trail or mountain to alert them about weather conditions or logistics for a ski competition, for example.
YouTube will also remind people about their subscriptions, alert them about new videos and show different versions of the site and different types of notifications based on the visitor's behavior.
They had, for example, called the police to alert them about their protest as it began, they were peaceful, and no one was hurt, merely inconvenienced, during the protest.
His reporting juices flowing, Allan sidled up to one of The Sun's soccer correspondents and suggested that one of them should rush back to the hotel — no cell phones in those days — call the office to alert them about a big story, and try to find a photographer to take some pictures of the English players sampling the local brew.
Letters will be sent to all potentially affected individuals alerting them about the security breach, the department said.
In late 2010, St . Judesent a letter to doctors alerting them about data showing that the silicone coating of the Riata lead could wear away.
Neither do we think that the making of a harassment warning could be considered a civil right within the meaning of Article 6 – it does not prohibit or force the subject to do anything, it simply alerts them about the complaint and warns them against future conduct.
But when the city relieved three officers of their posts after the fire, commanders complained that following the inspection schedule was all but impossible because no one ever alerted them about which buildings were under construction or demolition in their area.
It's tough to ignore a popup notification that your friend just watched a video called "Cat rides skateboard" – you're going to want to see for yourself, and then your friends will see an update alerting them about the video, creating an endless loop.
