The FCC’s rule changes detailed in a lengthy 2019 Report and Order governing RF exposure standards went into effect on May 3, 2021. The new rules do not change existing RF exposure (RFE) limits but do require that stations in all services, including amateur radio, be evaluated against existing limits, unless they are exempted. For stations already in place, that evaluation must be completed by May 3, 2023. After May 3 of this year, any new station, or any existing station modified in a way that’s likely to change its RFE profile — such as different antenna or placement or greater power — will need to conduct an evaluation by the date of activation or change.
Below is an excellent video by Dr. Gregory Lapin N9GL who reviews the change in depth.