Throughout the years there have been changes in technologies used to control insects and pests in herbaria. Fumigants were used in the past to protect specimens from insects. Many of these fumigants are now banned from use because they are known to be carcinogenic or otherwise harmful to people and the environment. One such fumigant formerly used by the Harvard University Herbaria was methyl bromide, which is now known to cause ozone depletion and is banned by the Montreal Protocol. Not only are many of the formerly used fumigants harmful to the people who used them, but over time the chemicals have burned through both paper and specimens. Another poison that was regularly used was arsenic, which was sprinkled on specimens to help kill insects and pests. While arsenic is no longer actively used, specimens that were treated with it remain in herbaria today.