Release of mercury from broken fluorescent bulbs

Mercury is a persistent, bioaccumulative toxin. Although the primary human exposure is from ingestion of fish contaminated with methyl mercury (HgCH3), exposures to elemental mercury vapor and mercury compounds via inhalation and dermal contact may also occur. Fluorescent bulbs contain mercury. Estimates of the amount of this mercury released when the bulbs are discarded and broken have varied widely. A new method was developed for measuring mercury released from broken bulbs. With the assumption that all mercury released is elemental vapor, it was found that between 17 and 40% of the mercury in broken low-mercury fluorescent bulbs is released to the air during a two-week period immediately following breakage, with higher temperatures contributing to higher release rates. One-third of the mercury release occurs during the first 8 hr after breakage. Many bulbs contain more mercury than the low-mercury bulbs tested. A typical discarded bulb releases between 3 and 8 mg of elemental mercury vapor over two weeks. Approximately 620 million fluorescent bulbs are discarded annually in the United States, and many are broken during disposal. Based on the estimated release rate of 3-8 mg per broken bulb developed in this study, discarded bulbs release approximately 2-4 tons of mercury per year in the United States. Waste management systems that minimize breakage before final disposal could reduce this total, as would the reduction of mercury content of bulbs. Elevated airborne levels of mercury could exist in the vicinity of recently broken bulbs, and under certain conditions, mercury concentrations could exceed occupational exposure limits.