Date of Award

January 2024

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Carrie A. Redlich

Second Advisor

Linda Cantley

Abstract

Introduction

The frequency and extent of environmental elemental mercury exposures in the U.S. are unknown. Due to its marked toxicity, elemental mercury has been phased out of many newer commercial products. However, mercury-containing products are still available, and a variety of religious, cultural, decorative, cosmetic, and illicit uses have been reported in the community. Small quantities of mercury can be highly toxic, and mercury toxicity can present nonspecifically and multi-systemically with the potential to be easily missed. Therefore, it is important to characterize the settings where mercury exposures occur and the extent of such exposures. The overall aim of this study is to describe and characterize mercury-related exposures in the U.S. occurring from 2018-2022, using data maintained by and available from the National Response Center, an emergency call center which fields initial calls for chemical, radiologic, biologic, and other environmental discharges (reported events with potential exposures). Specifically, this study aims to describe the frequency of mercury discharges, identify sources of mercury, characterize how these events occur, and identify industries currently involved in mercury discharges. Identifying possible sources of mercury, particularly those implicated in hazardous discharges, is important to prevent future exposures.

Methods

Data identified as mercury discharges between 2018-2022 was extracted from publicly available reports from the National Response Center, an emergency call center staffed by the U.S. Coast Guard which fields initial calls and reports for chemical, radiologic, biologic, and other environmental discharges. Data was extracted and stored in a Microsoft Excel file. Descriptive analyses were assisted with R statistical software and Microsoft Excel. Limited Chi-square analysis was performed to assess for differences among potential predictors such as region adjusted per capita and occupation vs home environmental settings. These limited analyses were not significant at a p<.05.

Results Between 2018-2022, 315 events were attributed to mercury discharges. A range of 58-70 events per year were recorded. Overall, 53.7% (n=169) occurred in the home environment, 47% (n=148) occurred in an occupational setting, and 13.7% (n=43) occurred in the outdoor environments, with some instances of crossover of categorization. Of all recorded mercury discharges, the majority were attributed to device leaks and breaks (n=157, 49.4%) or accidental spills (n=76, 23.9%). Of the 315 events, 39% of discharges (n=123) came from stored raw material. Miscellaneous non-electrical equipment accounted for 16.5% (n=52), including items such as barometers, antique decorative items like clocks, and boilers. Older healthcare devices such as thermometers and blood pressure kits accounted for 13.7% of discharges (n=43). Smaller percentages were attributable to lightbulbs and electrical equipment. Of the home environmental discharges (n=169), a large percentage were attribute d to stored raw materials such as jars of mercury (n=69, 40.8%). Occupational discharges (n=148) had similar findings, where stored raw material accounted for a larger percentage than other categories (n=56, 37.8%). Outdoor environmental discharges (n=43) also implicated a higher percentage of stored raw material (n=19, 44.2%). The majority of these reports involved 1-10 ounces of mercury (n=98, 63.6%), followed by small amounts <1 ounce (n=33, 21.4). Based on US Census Bureau Region population counts 2022, the number of events per capita among regions were similar. Considering mercury discharges in occupational settings (n=148) (Table 5), the most frequently implicated industries by OSHA Standard Industrial Classification (SIC) were non-industrial workplaces, most commonly the service sector (37.8%, n=56; includes schools, home services, and healthcare settings) and transportation/communications/electric/gas/sanitary services (28.4%, n=42).

Discussion

This data demonstrate that although mercury has been phased out of many products, it is still available in the community and results in a number of discharges in both the home and occupational setting. Most commonly, discharges, especially of concern in the home setting, are attributable to spills, leaks, and breaks from stored materials such as jars of mercury. It is unclear from the data why elemental mercury is being stored in homes. In the occupational setting, events have been primarily reported in non-industrial settings, such as schools, healthcare settings, and home services. Despite known industrial applications of elemental mercury, mining and construction accounted for fewer instances. The identification of sources of elemental mercury discharges is important to target preventive efforts, especially given the toxicity of even small quantities of elemental mercury and the non-specific presentation of mercury poisoning.

Comments

This is an Open Access Thesis.

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