This falls under a kind of implied consent so long as certain conditions are met. One, their contact information has to be readily available in a public format and not accompanied by any message stating they do not want unsolicited email. Two, the material sent to them has to be relevant to their capacity and duties in the workplace.
In other words, it has to be easy to find their email address and said address can't be accompanied by a 'don't contact me' sort of message, and you have to be sending something relevant to their job.
This is a really subjective part of the law where it would depend on the situation and the judge if it went to court. However, obviously you don't want to send a fashion piece to a sports journalist, and so on. If you aren't sure, then you can email them and ask for a clarification on their field of expertise and what it consists of, or find a safer bet. If you know it's not related to their job, don't send it.