Gun violence is a public health crisis in the United States. In 2017, 13 205 working-aged adults died from homicide by firearm, the ninth-leading cause of death in this age group. Overall, mortality due to gun-related causes among individuals 18 to 64 years of age exceeds that of motor vehicle crashes.

Despite the mortality and morbidity burden attributable to firearms, the United States has passed little federal legislation to regulate their purchase, distribution, storage, or use. Most firearm-related legislative activity has occurred at the state level. Since the early 1990s, every state has passed policies either strengthening or weakening restrictions on the sale, possession, and use of firearms. On average, states have become slightly more restrictive in their firearm policies in the past 30 years, particularly policies related to limitations on gun ownership among domestic violence offenders and other high-risk individuals, although many have become more permissive in areas such as “stand your ground” laws and concealed carrying of firearms.

From a public health perspective, the same structural barriers that have inhibited federal legislation on gun violence also restrict research into its determinants. However, a growing evidence base has documented the relationship between state-level firearm policy changes and firearm-associated homicide rates. These studies generally show that, at a population level, background checks and regulations for gun buyers (specifically permit to purchase) are associated with reductions in—although not elimination of—state-level firearm homicide rates, even after state-level social and demographic characteristics have been taken into account. There is less evidence of the relationship between firearm-related homicides and other types of gun control measures, such as limits on firearm trafficking or bans on assault weapons or high-capacity magazines. In addition, when states strengthen firearm policies intended to protect specific vulnerable populations (e.g., children, domestic violence victims), homicide rates in those groups tend to decline.

Each year, approximately 400 homicides by firearm occur when people are at work, accounting for about 9% of the approximately 4800 workplace fatalities occurring in the United States annually. In addition to mortality among victims, workplace homicide can lead to broader morbidity in the form of long-term trauma among coworkers, who are often witnesses and survivors. This trauma is exacerbated by witnesses’ need to return to the scene of the homicide each day to earn a living themselves.

In most research on workplace homicides, national surveillance data have been used to identify trends in rates and subgroups of workers at particular risk. A few small studies of employer-level determinants of workplace homicide have shown that homicides are more likely to occur at workplaces that permit weapons on site and under working conditions such as solo work at night or poor exterior lighting. However, higher-level determinants of workplace homicide are unknown. Specifically, to our knowledge, there has been no research on how the state-level policy environment is associated with the likelihood of being killed by another individual at work.

In this study, we assessed whether strengthening of state-level firearm laws from 2011 through 2017 was associated with decreases in state-level workplace homicide rates. Also, we tested for associations between changes in subcategories of firearm laws and workplace homicide rates.