Monitoring trends in lacrimator exposures using the National Poison Data System: 2000–2021

Abstract

Context:

Lacrimators are used by individuals for personal defense and by police for crowd control during periods of civil unrest. Increased public awareness about their use has raised concerns about their application and safety.

Objective:

To characterize patterns of lacrimator exposures in the United States, we describe temporal trends of calls to poison centers by demographics, substances, medical outcomes, exposure sites, and scenarios.

Methods:

A retrospective data analysis was performed for all single-substance lacrimator exposures in the United States reported to the National Poison Data System between 2000 and 2021. Descriptive analyses were performed to examine demographic characteristics, geographic distribution, product types and medical outcomes associated with lacrimator exposures.

Results:

A total of 107,149 lacrimator exposure calls were identified. There was an overall decrease in calls per year, from 6,521 calls in 2000 to 2,520 in 2020, followed by an increase to 3,311 calls in 2021. A declining trend was observed independent of total poison center call volume. Oleoresin capsicum was the most commonly reported substance (81,990, 76.5%). Individuals ages 19 years and younger accounted for 62% of calls, but adults ages 20 and over were more likely to develop major clinical effects (odds ratio 3.03; 95% confidence interval 1.91–4.81; P< 0.0001). The most common exposure site was “own residence,” followed by schools. School exposures accounted for 15.8% of exposures in children ages 6–12 years and 37.7% in adolescents. Among calls with documented scenarios, 19.7% involved unintentional exposures due to children accessing lacrimators.

Conclusion:

Lacrimator exposure calls to United States poison centers decreased from 2000 to 2021. Most calls pertain to oleoresin capsicum and individuals ages 19 and younger. Improper storage allowing children to have access to these chemicals, is a common scenario. Public safety interventions such as education about safe storage and use of lacrimators, improved product design, or regulatory changes may prevent unintentional exposures.

Introduction

Lacrimators, also referred to as crowd control agents or “tear gas,” have had an increased presence in society and the media as a result of their use during periods of civil unrest [1,2]. Lacrimators are commonly employed by civilian and military police, as well as individuals, as personal defence agents [3]. Frequently used substances in the United States (US) include oleoresin capsicum, referred to as “pepper spray,” chlorobenzylidene malononitrile, and chloroacetophenone, also known as Mace [4]. Chlorobenzylidene malononitrile replaced chloroacetophenone as the primary agent of use in “tear gas” in the 1950s because of lower toxicity (though chloroacetophenone is still used in some personal-defense sprays), and oleoresin capsicum became popular in the 1980s by police and the public [3]. Lacrimators were banned for warfare use by the 1997 entry into force of the international Chemical Weapons Convention. However, the ban included exceptions for lacrimator use by law enforcement [5,6].

When used, lacrimators are often employed as an aerosol to cover large areas but can also be a handheld spray for focused application [7]. These agents have irritant effects that can incapacitate an individual by acting on transient receptor potential (TRP) channels. Transient receptor potential channels are located throughout the human body in nociceptors and are widespread in the skin, cornea, conjunctiva, and mucous membranes. Two subtypes of transient receptor potential channels interact with lacrimators. Transient receptor potential vanilloid 1 (TRPV1) is targeted by oleoresin capsicum, while transient receptor potential ankyrin 1 (TRPA1) is targeted by the other agents [3]. These receptors play an important role in the body’s ability to sense environmental, chemical, and physical stimuli, such as heat and pain, while also playing roles in inflammation [8]. By stimulating transient receptor potential channels, lacrimators exert their negative health effects, including tearing, blepharospasm, rhinorrhea, and mucous membrane irritation. These symptoms are typically short-lived and resolve after the exposed person is decontaminated and removed from the source of exposure [7].

Significant effects can occur even with brief exposures, including chemical burns, corneal erosions, laryngospasm, and pulmonary edema [7]. Symptom severity is thought to be dose-dependent [9,10]. The release of lacrimators in enclosed spaces, such as rooms without proper ventilation or dense urban areas, can result in greater exposure doses [11,12]. Such high-dose exposures may lead to longer-lasting effects and the potential development of chronic respiratory symptoms [13,14]. Traumatic injuries associated with the use of lacrimators have been reported, such as physical injury from being hit by a tear gas canister, with significant morbidity, including blindness and loss of limbs [9,10].

While multiple reports and studies show potential chronic effects and varying exposures, there has not been a large national longitudinal study to describe the characteristics of these exposures over time [9,13–15]. This study aims to characterize individuals who reported exposure to lacrimators to the National Poison Data System (NPDS) from 2000 to 2021 and to describe overall trends, age groups at risk, and scenarios associated with lacrimator exposures.

Methods

We conducted a retrospective analysis of data from the National Poison Data System (NPDS), a surveillance system owned and operated by America’s Poison Centers. The NPDS collects exposure and information call data from the 55 poison centers in the United States. Although there were more than 60 poison centers in the US in the year 2000, data from centers that have closed since then were still included in this analysis. Poison centers provide free, 24 h professional advice and medical management information to the public and medical professionals on exposures to poisons, chemicals, drugs, and medications. Data are uploaded into NPDS in near-real-time. We queried NPDS for deidentified single substance human exposures to America’s Poison Centers generic category for lacrimators between 1 January 2000 and 31 December 2021. Substances in the query included capsicum defense sprays, chloroacetophenone, dibenz[b,f][1, 4]oxazepine, O-chlorobenzylidine malonitrile, and 10-chloro-5,10-dihydrophenarsazine, as well as generic codes for “other” and “unknown” lacrimators.

We conducted descriptive analyses of single substance lacrimator exposures by year, age, sex, specific lacrimator, exposure site, medical outcome, the highest level of health care facility care, and exposure scenario using SAS 9.4 (SAS Institute Inc, Cary, NC) and Excel (Microsoft Corporation, Redmond, WA). Odds ratios (OR) were calculated for associations between age and medical outcome or hospitalization. We categorized age (in years) by NPDS age categories with infants/toddlers (0–5), children (6–12), adolescents (13–19), adults (20–59), and older adults (60+). The Specialist in Poison Information receiving the call determined the exposure scenario and noted the events that led to the reported exposure (e.g., access to the product). However, scenario codes are not required for vapor exposures. We excluded calls in which the exposure was not responsible for the effect (coded as “Unrelated effect” or “Confirmed non-exposure”).

Results

From 1 January 2000 to 31 December 2021 there were a total of 107,149 calls regarding single-agent lacrimator exposures (Table 1). Most calls (n = 93,667, 87.4%) involved a person of known age. Of calls with known age, the majority were aged 19 and younger (58,103, 62.0%). Adults aged 20–59 were reported to have been exposed in 32,847 calls (35.1%), and adults aged 60 and older had reported exposures in 2,717 calls (2.9%). Exposures of infants/toddlers ≤5 years of age accounted for 20,162 calls (21.5% of those with known age), while exposures of children aged 6–12 years were reported in 18,976 calls (20.3%), and exposures of adolescents aged 13–19 were reported in 18,965 calls (20.2%). Sex was recorded in 101,861 calls (95%); 54,186 (53.1%) of exposed people were male, and 47,675 were female (46.8%) (Table 1), of whom 216 were pregnant (0.5%).

Table 1.

Characteristics of lacrimator exposures by age, substance, and sex.

	Number of calls	%
Total exposures	107,149
Age
≤5	20,162	18.8%
6–12	18,976	17.7%
13–19	18,965	17.7%
20–59	32,847	30.7%
≥60	2717	2.5%
Unknown or other	13,482	12.6%
Lacrimator
Oleoresin capsicum	81,990	76.5%
Chloroacetophenone	18,954	17.7%
Chlorobenzylidene malononitrile	1054	1.0%
Other	5151	4.8%
Sex
Male	54,186	50.6%
Female	47,675	44.5%
Unknown	5288	4.9%

Percentages for age and sex categories were calculated using total exposures as the denominator.

There was an overall decrease in exposure calls over time, with 6,521 calls in 2000 and 2520 exposure calls in 2020. In 2021, there were 3,311 exposures, although it is unknown whether this may indicate a change to an increasing trend. The year 2001 had the most lacrimator exposure calls at 7,025, and 2020 had the fewest. This decrease is independent of total human exposure call volume to poison centers (Figure 1). When comparing the percent of lacrimator exposure calls per year to total exposure calls, the decreasing trend remains (Figure 2) [16]. Declines were observed among adults ages 20–59 (1,287 calls absolute decrease, 58.5% relative decrease), adolescents ages 13–19 (579 calls absolute decrease, 60.9% relative decrease), and infants/toddlers ages 5 and under (857 calls absolute decrease, 54.2% relative decrease). Calls for children ages 6 to 12 also decreased during this time (439 calls absolute decrease, 61.8% relative decrease). Calls pertaining to older adults increased slightly (21 calls absolute increase, 18.8% relative increase; Figure 3).

Figure 1.

Lacrimator exposures and total human exposures reported to United States poison centers, 2000–2021.

Figure 2.

Changes in annual call volumes for lacrimators and total human exposures reported to United States poison centers, relative to calendar year 2000.

Figure 3.

Lacrimator exposures by age group over time, 2000–2021.

During this timeframe, the agent oleoresin capsicum was associated with the highest number of calls at 81,990 exposures (76.5%), followed by chloroacetophenone at 18,954 (17.7%), chlorobenzylidene malononitrile at 1,054 (1.0%) and “other” at 5,151 (4.8%) (Table 1). There were only four exposure calls coded for dibenz[b,f][1, 4]oxazepine and one call for 10-chloro-5,10-dihydrophenarsazine. While the total number of oleoresin capsicum calls decreased from 4,553 calls in 2001 to 3037 in 2021, the proportion of oleoresin capsicum calls relative to the total number of lacrimator calls increased over the study period from 69.8% of calls in 2000 to 92.8% in 2021. From 2000 to 2011, chloroacetophenone represented 19.4% to 23.6% of calls but then declined over the next several years (Figure 4). Chlorobenzylidene malononitrile also decreased from a peak of 2.2% of calls in 2000 down to 0.5% of calls in 2021. Other agents represented 4.8% of calls over the study period (range: 2.5–6.8%).

Figure 4.

Annual lacrimator exposures reported to United States poison centers by active ingredient, 2000–2021.

The most reported exposure site was “own residence” (n = 68,668, 64.1%), followed by school (n = 11,526, 10.8%) and public area (n = 9,981, 9.3%). Approximately 4.7% (n = 5,023) occurred in a workplace. Approximately 15.8% (n = 2,992) of exposures in children ages 6–12 years and 37.7% (n = 7,157) in adolescents occurred in schools, compared with less than 1% in adults ages 20–59 (n = 308), adults aged 60 and over (n = 15), or infants/toddlers (n = 134) (Table 2), though “own residence” was still the most common site of exposure in all age groups.

Table 2.

Reported sites of lacrimator exposures by age group.

Exposure site	Age ≤5		Age 6–12		Age 13–19		Age 20–59		Age ≥60		Unknown/other		Total
Own residence	17,862	88.6%	13,414	70.7%	7,964	42.0%	20,389	61.1%	2,156	79.4%	6,883	51.1%	68,668	64.1%
Other residence	890	4.4%	933	4.9%	627	3.3%	965	2.9%	104	3.8%	415	3.1%	3,934	3.7%
School	134	0.7%	2,992	15.8%	7,157	37.7%	308	0.9%	15	0.6%	920	6.8%	11,526	10.8%
Workplace	25	0.1%	39	0.2%	276	1.5%	3,051	9.3%	105	3.9%	1,526	11.3%	5,022	4.7%
Public area	630	3.1%	876	4.6%	1,736	9.2%	4,819	14.7%	212	7.8%	1,708	12.7%	9,981	9.3%
Restaurant / food service	44	0.2%	28	0.1%	46	0.2%	200	0.6%	9	0.3%	209	1.6%	536	0.5%
Health care facility	24	0.1%	22	0.1%	46	0.2%	123	0.4%	14	0.5%	244	1.8%	473	0.4%
Other	423	2.1%	552	2.9%	426	2.2%	1,094	3.3%	71	2.6%	513	2.8%	3,079	2.9%
Unknown	129	0.6%	120	0.6%	687	3.6%	1,898	5.8%	31	1.1%	1,064	7.9%	3,929	3.7%
Total	20,161		18,976		18,965		32,847		2,717		13,482		107,149	100.00%

At least one associated exposure scenario was recorded in 6,358 (5.9%) calls; of these, 6,052 (95.2%) calls reported one associated exposure scenario, 284 (4.5%) calls reported two associated exposure scenarios, and 22 (0.3%) calls reported three exposure scenarios, for a total of 6,686 exposure scenarios (Table 3). As scenario coding is not required, only 5.9% of lacrimator exposure calls had a documented scenario. Of reported scenarios, 1,315 (19.7%) were associated with children or pets gaining access to lacrimators or otherwise inappropriate storage (398 of “child caused exposure,” 368 of “child or pet accessed medication/product from a purse,” and 549 of “stored within sight of a child”), while 1,810 (27.1%) involved apparent accidental or unintentional exposure from use of lacrimators nearby (378 of “drift from an adjacent area or ventilation system,” and 1,432 of “exposure to product fumes/vapors in a poorly ventilated area”).

Table 3.

Common scenarios associated with lacrimator exposures reported to the National Poison data System.

Scenario	n = 6,686	%
Child caused exposure (gave to sibling or pet, etc.)	398	6.0%
Child or pet accessed medication / product from purse	368	5.5%
Stored within sight of child	549	8.2%
Exposure to product fumes / vapors in a poorly ventilated area	1,432	21.4%
Drift from adjacent area or ventilation system	378	5.7%
Other gas / fume / vapor exposure	1,224	18.3%
Aerosol sprayed in face	659	9.9%
Other scenarios not listed above	1,678	25.1%

A known medical outcome was recorded in 58,369 calls (54.5%). Of these, the majority of exposures resulted in minor effects (49,684, 85.1%). Major effects accounted for 0.1% of exposures, with 79 calls reported (Table 4). Among calls followed to a known outcome, adults ages 20 and over were significantly more likely than those aged 19 and younger to develop major clinical effects (OR 3.03; 95% confidence interval [CI]: 1.91–4.81; P < 0.0001). Of 48,780 calls not followed to a known outcome, 44,286 (90.8%) were not followed due to the specialist in poison information judging minimal clinical effects possible, and 947 (1.9%) were judged as non-toxic exposure with clinical effects not expected. Calls pertaining to adults aged 20 years and older were less likely to be followed to a known outcome than calls describing pediatric exposures (OR 0.76; 95% CI: 0.74–0.78; P < 0.0001).

Table 4.

Medical outcomes of lacrimator exposures by age group.

Medical outcome	Age ≤5	%	Age 6–12	%	Age 13–19	%	Age 20–59	%	Age ≥60	%	Unknown/Other	%	Total	%
Major effect	13	0.1%	8	0.04%	8	0.04%	43	0.1%	4	0.2%	3	0.02%	79	0.07%
Minor effect	10,406	51.6%	9,837	51.8%	8,696	45.9%	13,926	42.4%	1,247	45.9%	5,572	41.3%	49,684	46.4%
Moderate effect	535	2.7%	631	3.3%	1,028	5.4%	2,151	6.6%	163	6.0%	504	3.7%	5,012	4.7%
No effect	962	4.8%	600	3.2%	999	5.3%	599	1.8%	78	2.9%	356	2.6%	3,594	3.4%
Not followed, judged as nontoxic exposure (clinical effects not expected)	279	1.4%	143	0.8%	170	0.9%	160	0.5%	20	0.7%	175	1.3%	947	0.9%
Not followed, minimal clinical effects possible (no more than minor effect possible)	7,602	37.7%	7,411	39.1%	7,520	39.7%	14,647	44.6%	1,153	42.4%	5,953	44.2%	44,286	41.3%
Unable to follow, judged as potentially toxic exposure	365	1.8%	346	1.8%	544	2.9%	1,321	4.0%	52	1.9%	919	6.8%	3,547	3.3%
Total	20,162		18,976		18,965		32,847		2,717		13,482		107,149

There were 20,358 (19.0%) calls referred to or originating from a healthcare facility. Of these, 15,699 (77.1%) were treated/evaluated and released, while 128 (0.6%) were admitted to a critical care unit, 213 (1.0%) were admitted to non-critical care unit, and 86 (0.4%) were admitted to a psychiatric facility (Table 5). The remaining 4,232 (20.8%) calls were documented as “Lost to follow-up/left AMA (Discharged against medical advice)” or “Refused referral/did not arrive at [Health Care Facility]. Adults who were exposed to lacrimators were significantly more likely to be admitted to either a critical care or non-critical care unit compared to exposed individuals aged 19 years or less (OR 1.69; 95% CI: 1.33–2.14; P < 0.0001). Patients admitted to a critical care or non-critical care unit were more likely to be adults aged 60 and greater, compared to other age groups (OR 2.39; 95%CI: 1.47–3.89; P < 0.001).

Table 5.

Level of health care received by age group.

Level of health care	Age ≤5	%	Age 6–12	%	Age 13–19	%	Age 20–59	%	Age ≥60	%	Unknown/other	%	Total	%
Admitted to critical care unit	25	0.8%	9	0.4%	15	0.4%	64	0.8%	9	1.9%	6	0.2%	128	0.6%
Admitted to noncritical care unit	21	0.7%	12	0.6%	27	0.8%	109	1.3%	9	1.9%	35	1.3%	213	1.1%
Admitted to psychiatric facility	2	0.1%	0	0%	18	0.5%	52	0.6%	1	0.2%	13	0.5%	86	0.4%
Patient lost to follow-up / left against medical advice	312	10.3%	333	15.3%	457	13.5%	1,258	14.8%	58	12.4%	698	25.1%	3,116	15.3%
Patient refused referral / did not arrive at health care facility	97	3.2%	78	3.6%	180	5.3%	586	6.9%	24	5.1%	151	5.4%	1,116	5.5%
Treated / evaluated and released	2,564	84.9%	1,750	80.2%	2,686	79.4%	6,456	75.7%	366	78.4%	1,877	67.5%	15,699	77.1%
Total	3,021		2,182		3,383		8,525		467		2,780		20,358

Discussion

Exposure to lacrimators reported to poison centers in the US declined from 2000 to 2021, with most of the absolute and relative decline in calls about adults aged 20 to 59, infants/toddlers aged 5 and under, and adolescents aged 13 to 19. It is unclear what led to the decline in lacrimator exposures reported to poison centers. Potential explanations could be increased familiarity with exposures among users, stricter legislation of “pepper spray” use and availability, decreased sales of pepper spray products, or a decrease in the actual use of lacrimators. Unfortunately, there are no studies identified that could help clarify the reason(s) for the decline. There were more lacrimator exposures reported in 2021 compared to 2020, although it is unknown whether this may represent a change to an increasing trend.

Exposure sites appear to reflect where patients spend most of their time. Exposure at “Own residence” was most commonly reported for all age groups. “School” was the second most common site in calls about school-aged children (6–19 years), accounting for 37.7% of exposures. School settings are likely to have a higher density of similarly aged individuals present in a confined space, allowing for the release of a lacrimator to affect substantially more people compared to a lacrimator release in the home. Adults aged 20–59 years were commonly exposed in “Public Area” (14.7%) or “Workplace” (9.3%).

Of the small minority of calls that included an exposure scenario, scenarios associated with unintentional exposures from children accessing lacrimators appeared relatively common. Additionally, a relatively large proportion of calls with scenarios of “exposure to product fumes/vapors in a poorly ventilated area” (1,432, 21.4%) and “drift from an adjacent area or ventilation system” (378, 5.7%) suggests that many exposures to lacrimators may be unintentional. One limitation associated with scenario coding is the fact that it is not a required field in NPDS, and only 5.9% of total lacrimator exposure calls had a documented scenario.

Overall, few calls reported that the exposed person developed a serious medical outcome or required hospitalization. Adults aged 20 and older had higher odds of both “major” medical outcomes and admission to a hospital floor or intensive care unit. Admitted patients were also more likely to be adults aged 60 and greater. It is unclear if this pattern is because adults are more susceptible than pediatric patients to the effects of lacrimators or relative over-reporting of mild or minimally symptomatic pediatric patients compared to adults. Adults may also be more likely to receive higher doses than young children, who may not be able to fully depress the nozzle of a spray can during unintentional play.

The findings in this report are subject to several limitations. The NPDS relies on data voluntarily reported to poison centers by healthcare providers and the public; therefore, NPDS does not capture all exposures, and the true denominator of exposed people is unknown. Exposed people with only mild symptoms may be less inclined to seek medical care or contact a poison center, so more severely ill persons may be relatively overrepresented in NPDS data. This may be particularly relevant in pediatric calls, as parents or guardians may be more concerned and likely to report mild exposures in children than exposures affecting themselves or other adults. National Poison Data System data are captured during real-time clinical management of acutely exposed patients. While quality assurance processes are in place at each center and NPDS, human error in data entry is possible. In addition, the type of lacrimator is self-reported and not confirmed by clinical tests or environmental sampling. Therefore, callers may think they were exposed to a lacrimator when they were not. Chloroacetophenone and oleoresin capsicum are chemically distinct products with different identification codes in the product database used for NPDS coding. However, callers may not differentiate between the two compounds, and this may affect the way poison center staff code the information. It is possible that many people who called poison centers were unclear about the specific substance, possibly because they did not read or have access to product packaging.

Further confusing the matter, the brand name Mace was originally used for marketing an aerosolized chloroacetophe-none-based personal defense spray, but in recent years, personal defense sprays containing oleoresin capsicum have become more widely available for purchase in the US than products containing chloroacetophenone [17]. Finally, data surrounding the scenario of lacrimator exposure, such as the situation that led to the exposure or the ventilation of the exposure site, were only reported for 5.9% of calls. Having these details would aid in identifying risk factors for future exposures and allow for timely and targeted interventions.

Conclusions

The number of lacrimator exposures reported to US poison centers has decreased over the past 22 years, both in terms of absolute calls and the percentage of all calls to poison centers. Oleoresin capsicum is the most commonly reported agent and represents an increasing proportion of exposures relative to chloroacetophenone, chlorobenzylidene malononitrile, and other agents. While most calls are about those aged 19 and younger, adults aged 20 and over appear more likely to develop major clinical effects and be admitted to hospitals. Most exposures occur at home, though exposures in schools are relatively more common in adolescents and children. Approximately one-fifth of exposures were reported in children, possibly related to improper storage allowing children to have access. Future public health interventions emphasizing safe storage and use of lacrimators may help prevent unintentional exposures.