Peace be upon you. According to Grand Ayatollah Khamenei (may Allah protect him), if the impure item is something used for eating or drinking, it is necessary to inform others. If it is something that would affect the validity of ablution or washing, it is also necessary to inform them as a precaution. Otherwise, there is no obligation to inform. According to Grand Ayatollah Sistani (may Allah protect him), informing is only required if failing to do so would lead to violating a prohibition, such as using impure cooking utensils for eating or drinking, or a mandatory act, like using impure water for ablution or washing. Thank you, and may you be successful in all good.