Deported, homeless, and into the canal: Environmental structural violence in the binational Tijuana River

Illicit Fentanyl Use and Hepatitis C Virus Seroconversion Among People Who Inject Drugs in Tijuana and San Diego: Results From a Binational Cohort Study

BACKGROUND

Illicitly manufactured fentanyl (IMF) increases overdose mortality, but its role in infectious disease transmission is unknown. We examined whether IMF use predicts hepatitis C virus (HCV) and human immunodeficiency virus (HIV) incidence among a cohort of people who inject drugs (PWID) in San Diego, California and Tijuana, Mexico.

METHODS

PWID were recruited during 2020-2022, undergoing semi-annual interviewer-administered surveys and HIV and HCV serological rapid tests through 2024. Cox regression was conducted to examine predictors of seroconversion considering self-reported IMF use as a 6-month lagged, time-dependent covariate.

RESULTS

Of 398 PWID at baseline, 67% resided in San Diego, 70% were male, median age was 43 years, 42% reported receptive needle sharing, and 25% reported using IMF. HCV incidence was 14.26 per 100 person-years (95% confidence interval [CI]: 11.49-17.02), and HIV incidence was 1.29 (95% CI: .49-2.10). IMF was associated with HCV seroconversion, with a univariable hazard ratio (HR) of 1.64 (95% CI: 1.09-2.40), and multivariable HR of 1.57 (95% CI: 1.03-2.40). The direction of the relationship with HIV was similar, albeit not significant (HR 2.39; 95% CI: .66-8.64).

CONCLUSIONS

We document a novel association between IMF and HCV seroconversion among PWID in Tijuana-San Diego. Few HIV seroconversions (n = 10) precluded our ability to assess if a similar relationship held for HIV. IMF's short half-life may destabilize PWID-increasing the need for repeat dosing and sharing smoking materials and syringes. New preventive care approaches may reduce HCV transmission in the fentanyl era.

Safe Injection Self-Efficacy is Associated with HCV and HIV Seropositivity Among People Who Inject Drugs in the San Diego-Tijuana Border Region

Safe injection self-efficacy (SISE) is negatively associated with injection risk behaviors among people who inject drugs (PWID) but has not been examined in differing risk environments. We compared responses to a validated SISE scale between PWID in San Diego, California and Tijuana, Mexico, and examine correlates of SISE among PWID in Tijuana. PWID were recruited via street outreach for a longitudinal cohort study from October 2020-September 2021. We compared SISE scale items by city. Due to low variability in SISE scores among San Diego residents, we restricted analysis of factors associated with SISE to Tijuana residents and identified correlates of SISE score levels (low, medium, high) using ordinal logistic regression. Of 474 participants, most were male (74%), Latinx (78%) and Tijuana residents (73%). Mean age was 44. Mean SISE scores among San Diego residents were high (3.46 of 4 maximum) relative to Tijuana residents (mean: 1.93). Among Tijuana residents, White race and having previously resided in San Diego were associated with higher SISE scores. HCV and HIV seropositivity, homelessness, fentanyl use, polysubstance co-injection, and greater injection frequency were associated with lower SISE scores. We found profound inequalities between Tijuana and San Diego SISE, likely attributable to differential risk environments. Associations with fentanyl and polysubstance co-injection, injection frequency, and both HIV and HCV seropositivity suggest that SISE contribute to blood-borne infection transmission risks in Tijuana. SISE reflects an actionable intervention target to reduce injection risk behaviors, but structural interventions are required to change the risk environment.

Safe Injection Self-Efficacy is associated with HCV and HIV seropositivity among people who inject drugs in the San Diego-Tijuana border region

Background

Safe injection self-efficacy (SISE) is negatively associated with injection risk behaviors among people who inject drugs (PWID) but has not been examined in differing risk environments. We compared responses to a validated SISE scale between PWID in San Diego, California and Tijuana, Mexico, and examine correlates of SISE among PWID in Tijuana.

Methods

PWID were recruited via street outreach for a longitudinal cohort study from October 2020 - September 2021. We compared SISE scale items by city. Due to low variability in SISE scores among San Diego residents, we restricted analysis of factors associated with SISE to Tijuana residents and identified correlates of SISE scores (low, medium, high) using ordinal logistic regression.

Results

Of 474 participants, most were male (74%), Latinx (78%) and Tijuana residents (73%). Mean age was 44. Mean SISE scores among San Diego residents were high (3.46 of 4 maximum) relative to Tijuana residents (mean: 1.93). Among Tijuana residents, White race and having previously resided in San Diego were associated with higher SISE scores. HCV and HIV seropositivity, homelessness, fentanyl use, polysubstance co-injection, and greater injection frequency were associated with lower SISE scores.

Conclusions

We found profound inequalities between Tijuana and San Diego SISE, likely attributable to differential risk environments. Associations with fentanyl and polysubstance co-injection, injection frequency, and both HIV and HCV seropositivity suggest that SISE contribute to blood-borne infection transmission risks in Tijuana. SISE reflects an actionable intervention target to reduce injection risk behaviors, but structural interventions are required to intervene upon the risk environment.

A brief instrument measuring the water, sanitation and hygiene domain of menstrual health among women who inject drugs

BACKGROUND

Domains of adequate menstrual health (MH) include access to water, sanitation, and hygiene (WASH). People who menstruate with social disadvantages-such as homelessness or drug injection practices-often face barriers to WASH access. However, validated instruments to measure MH are limited among marginalized populations, and available instruments involve lengthy surveys. We developed and evaluated psychometric properties of a novel 'MH WASH Domain Scale-12' among people who menstruate and who inject drugs in the Tijuana-San Diego region and identified correlates of MH access using this scale.

METHODS

We constructed a MH-scale based on access to twelve WASH-related items: (1) menstrual products, (2) body hygiene (bathing per week), (3) water sources for bathing, (4) improved, (5) non-shared, (6) available, (7) private, (8) nearby, (9) and safe sanitation facilities, (10) availability of soap, (11) water source for handwashing, and (12) handwashing facilities with soap/water. Variables were dichotomized and summed, with scores ranging from 0-12 points and higher scores indicating better MH access. We assessed the scale's reliability and construct and content validity using data from a binational cross-sectional study. The sample included people who inject drugs (PWID) who had ever menstruated in their lifetime and were 18+ during 2020-2021. MH-WASH items were described, and the scale was further used as an outcome variable to identify correlates.

RESULTS

Among 125 (124 cis-female and 1 trans-male) PWID that reported menstruating, our 'MH WASH Domain Scale-12' was reliable (Cronbach's alpha = 0.81, McDonald's Omega total = 0.83) and valid. We identified two sub-domains: Factor-1 included items describing 'WASH availability' and Factor-2 contained items related to 'WASH security'-encompassing physical and biological safety. Scale scores were significantly lower among participants experiencing unsheltered homelessness compared to participants experiencing sheltered homelessness or living in permanent housing.

CONCLUSION

We constructed and validated a novel and reliable scale to measure MH-related WASH access that can be used to assess MH among marginalized populations in English- and Spanish-speaking contexts. Using this scale we identified disparities in MH-WASH access among PWID and who menstruate in the US-Mexico border region.

Water, sanitation, and hygiene access among people who inject drugs in Tijuana and San Diego in 2020-2021: a cross-sectional study

BACKGROUND

Water, sanitation, and hygiene (WASH) access is critical to public health and human dignity. People who inject drugs (PWID) experience stigma and structural violence that may limit WASH access. Few studies have assessed WASH access, insecurity, and inequities among PWID. We describe WASH access, social and geographic inequalities, and factors associated with WASH insecurity among PWID in the Tijuana-San Diego metropolitan area.

METHODS

In this cross-sectional binational study, we interviewed PWID (age 18+) in 2020-2021 about WASH access and insecurity. City of residence (Tijuana/San Diego) and housing status were considered as independent variables to describe key WASH access outcomes and to assess as factors associated with WASH insecurity outcomes. Measures of association between outcomes and independent variables were assessed using log modified-Poisson regression models adjusting for covariates.

RESULTS

Of 586 PWID (202 Tijuana; 384 San Diego), 89% reported basic access to drinking water, 38% had basic hand hygiene, 28% basic sanitation, and 46% access to bathing, and 38% reported recent open defecation. Participants residing in Tijuana reported significantly higher insecurity in accessing basic drinking water (aRR: 1.68, 95%CI: 1.02-2.76), basic hygiene (aRR: 1.45, 95%CI: 1.28-1.64), and bathing (aRR: 1.21, 95%CI: 1.06-1.39) than those living in San Diego. Participants experiencing unsheltered homelessness experienced significantly higher insecurity in accessing basic drinking water (aRR: 2.03, 95%CI: 1.07-3.86), basic sanitation (aRR: 1.68, 95%CI: 1.48, 1.92), bathing (aRR: 1.84, 95%CI: 1.52-2.22), and improved water sources for cleaning wounds (aRR: 3.12, 95%CI: 1.55-6.29) and for preparing drugs (aRR: 2.58, 95%CI: 1.36-4.89) than participants living in permanent housing.

CONCLUSION

WASH access among PWID in the Tijuana-San Diego metropolitan area was low by international standards and lower than the national averages in both countries. Homelessness was significantly associated with WASH insecurity in this population. Concentrated efforts are needed to guarantee continuously available WASH services for PWID-especially those who are unsheltered.

Seeking care across the US-Mexico border: The experiences of Latinx and Indigenous Mexican caregivers of children with asthma or respiratory distress

BACKGROUND

Many Latinx and Indigenous Mexican populations in the United States Southwest live in unincorporated communities in the US-Mexico borderlands called colonias. These environmental justice communities often lack basic infrastructure, including healthcare services, prompting many to seek services across the border. However, due to geopolitical factors more vulnerable caregivers are limited to utilize healthcare services in the US. This paper reports the experiences and healthcare decision-making of caregivers living in colonias in the US-Mexico border region who care for children with respiratory health conditions.

METHODS

This study was carried out from September to December 2020. Focus groups and interviews were conducted with Latinx and Indigenous Mexican caregivers of children with asthma or respiratory distress. Qualitative interviews elicited caregivers' perspectives on the environmental factors affecting children's chronic health conditions and use of healthcare services. The analysis employed the concept of structure vulnerability to theorize geography as a structural determinant of health for caregivers faced with making healthcare decisions for their suffering from respiratory health conditions. A survey was administered to collect basic sociodemographic information.

RESULTS

A total of 36 caregivers participated in the study. Structural factors including unincorporated community status and government inaction intersected with social determinants of health to prompt caregivers to cross the US-Mexico border to access healthcare services in Mexico for their children. Yet, more vulnerable caregivers (i.e., those without documentation status in the US) and their children, accessing healthcare services in the US was not an option limiting caregivers' ability to meet their children's healthcare needs. In such cases, geography acts as a structural determinant of health.

CONCLUSION

This study shows the importance of geography in health. Rural unincorporated colonias located in the borderlands are precariously located and lack basic critical infrastructure including healthcare access. Within such places, historically and socially marginalized populations become invisible, are subject to the health effects of environmental hazards, and are limited depending on their positionality and thus vulnerability to healthcare services.

WaSH insecurity and anxiety among people who inject drugs in the Tijuana-San Diego border region

BACKGROUND

Water, sanitation, and hygiene (WaSH) insecurity increases the risk of water-related diseases. However, limited research has been conducted on psychosocial distress as it relates to WaSH insecurity, especially among people who inject drugs (PWID). We examined the relationship between WaSH insecurity and related anxiety among PWID living in different housing conditions along the US-Mexico border region.

METHODS

From 2020-2021, a cross-sectional study was conducted among 585 people who injected drugs within the last month in Tijuana (N = 202), San Diego (N = 182), and in both Tijuana and San Diego (N = 201). Participants underwent interviewer-administered surveys related to WaSH access, substance use, and generalized anxiety disorder (GAD-7). Quasi-Poisson regressions were used to assess associations between WaSH insecurity and anxiety in the prior 6-months.

RESULTS

Participants were 75% male, 42% were unhoused and 91% experienced WaSH insecurity in the prior 6-months. After adjusting for housing status, gender, and age, lack of access to basic drinking water (Adj RR: 1.28; 95% CI: 1.02-1.58), sanitation (Adj RR:1.28; 95% CI: 1.07-1.55), and a daily bath/shower (Adj RR: 1.38; 95% CI: 1.15-1.66) were associated with mild-severe anxiety. The number of WaSH insecurities was independently associated with a 20% increased risk of experiencing anxiety per every additional insecurity experienced (Adj RR: 1.20; CI: 1.12-1.27). We also found a significant interaction between gender and housing status (p = 0.003), indicating that among people experiencing sheltered/unsheltered homelessness, women had a higher risk of mild-severe anxiety compared to men (Adj RR: 1.55; 95% CI: 1.27-1.89). At the same time, among women, those who are unhoused have 37% increased risk of anxiety than those who live in stable housing conditions (Adj RR: 1.37; 95% CI: 1.01-1.89).

CONCLUSION

The lack of specific WaSH services, particularly lack of drinking water, toilets, and daily showers were associated with higher levels of anxiety among PWID in the Tijuana-San Diego border region. Women experiencing homelessness were especially vulnerable. WaSH interventions that provide safe, 24-h access may help to reduce anxiety and health risks associated with WaSH insecurity.

Evidence of transboundary movement of chemicals from Mexico to the U.S. in Tijuana River Estuary sediments

The Tijuana River Estuary (TRE) has been a public health hazard and point of contention between the United States and Mexico for decades, with sources of pollution on both sides of the border. The goal of our study is to determine the presence and dynamics of chemical contamination in the TRE. We sampled sediment from four TRE locations in the U.S. during stable dry conditions and immediately after a wet weather period. Organic chemicals were initially screened with non-targeted analysis using gas chromatography high-resolution mass spectrometry (GC/HRMS) that tentatively identified 6978 chemicals in the NIST 20 database. These tentative identifications were filtered using the USEPA CompTox database to guide quantitative targeted analysis at detection limits below 1 ng/g dry weight sediment. Quantitative targeted analysis of 152 organic pollutants and 18 inorganic elements via GC/HRMS revealed generally higher concentrations of contaminants in dry weather sediments compared to wet weather sediments. The highest concentrations of all chemical classes were detected at the site closest to the U.S.-Mexico border, followed by an urban area near Imperial Beach, California, U.S. All sites exhibited a mixture of petrogenic and pyrogenic polycyclic aromatic hydrocarbons (PAHs). Current-use pesticides were dominated by pyrethroid insecticides and the thiocarbamate herbicide s-Ethyl dipropylthiocarbamate (EPTC), while the U.S.-banned organochlorine pesticides were dominated by chlordanes, dieldrin, and dichlorodiphenyltrichloroethane (DDT) and its degradation byproducts. Polychlorinated biphenyl (PCB) concentrations were greatest at the site closest to the U.S.-Mexico border but in the low nanogram-per-gram range. Phthalates were only found at the same site, with relatively high concentrations of bis(2-ethylhexyl) phthalate. This study provides positive identification and quantitative concentrations for organic pollutants in TRE sediments. Our data suggest that there are multiple sources of chemical contamination in the estuary, including possible transboundary movement of pollutants from Mexico.

Fentanyl, heroin, and methamphetamine-based counterfeit pills sold at tourist-oriented pharmacies in Mexico: An ethnographic and drug checking study

BACKGROUND

Fentanyl- and methamphetamine-based counterfeit prescription drugs have driven escalating overdose death rates in the US, however their presence in Mexico has not been assessed. Our ethnographic team has conducted longitudinal research focused on illicit drug markets in Northern Mexico since 2018. In 2021-2022, study participants described the arrival of new, unusually potent tablets sold as ostensibly controlled substances, without a prescription, directly from pharmacies that cater to US tourists.

AIMS

To characterize the availability of counterfeit and authentic controlled substances at pharmacies in Northern Mexico available to English-speaking tourists without a prescription.

METHODS

We employed an iterative, exploratory, mixed methods design. Longitudinal ethnographic data was used to characterize tourist-oriented micro-neighborhoods and guide the selection of n=40 pharmacies in n=4 cities in Northern Mexico. In each pharmacy, samples of "oxycodone", "Xanax", and "Adderall" were sought as single pills, during English-language encounters, after which detailed ethnographic accounts were recorded. We employed immunoassay-based testing strips to check each pill for the presence of fentanyls, benzodiazepines, amphetamines, and methamphetamines. We used Fourier-Transform Infrared Spectroscopy to further characterize drug contents.

RESULTS

Of n=40 pharmacies, one or more of the requested controlled substances could be obtained with no prescription (as single pills or in bottles) at 28 (70.0%) and as single pills at 19 (47.5%). Counterfeit pills were obtained at 11 pharmacies (27.5%). Of n=45 samples sold as one-off controlled substances, 18 were counterfeit. 7 of 11 (63.6%) samples sold as "Adderall" contained methamphetamine, 8 of 27 (29.6%) samples sold as "Oxycodone" contained fentanyl, and 3 "Oxycodone" samples contained heroin. Pharmacies providing counterfeit drugs were uniformly located in tourist-serving micro-neighborhoods, and generally featured English-language advertisements for erectile dysfunction medications and "painkillers". Pharmacy employees occasionally expressed concern about overdose risk and provided harm reduction guidance.

DISCUSSION

The availability of fentanyl-, heroin-, and methamphetamine-based counterfeit medications in tourist-oriented independent pharmacies in Northern Mexico represents a public health risk, and occurs in the context of 1) the normalization of medical tourism as a response to rising unaffordability of healthcare in the US, 2) plummeting rates of opioid prescription in the US, affecting both chronic pain patients and the availability of legitimate pharmaceuticals on the unregulated market, 3) the rise of fentanyl-based counterfeit opioids as a key driver of the fourth, and deadliest-to-date, wave of the opioid crisis. It was not possible to distinguish counterfeit medications based on appearance of pills or geography of pharmacies, because identically-appearing authentic and counterfeit versions were often sold in close geographic proximity. Nevertheless, people who consume drugs may be more trusting of controlled substances purchased directly from pharmacies. Due to Mexico's limited opioid overdose surveillance infrastructure, the current death rate from these substances remains unknown.

Drug checking in the fentanyl era: Utilization and interest among people who inject drugs in San Diego, California

BACKGROUND

In North America, overdose rates have steeply risen over the past five years, largely due to the ubiquity of illicitly manufactured fentanyls in the drug supply. Drug checking services (DCS) represent a promising harm reduction strategy and characterizing experiences of use and interest among people who inject drugs (PWID) is a priority.

METHODS

Between February-October 2022, PWID participating in a cohort study in San Diego, CA and Tijuana, Mexico completed structured surveys including questions about DCS, socio-demographics and substance use behaviors. We used Poisson regression to assess factors associated with lifetime DCS use and characterized experiences with DCS and interest in free access to DCS.

RESULTS

Of 426 PWID, 72% were male, 59% Latinx, 79% were experiencing homelessness and 56% ever experienced a nonfatal overdose. One third had heard of DCS, of whom 57% had ever used them. Among the latter, most (98%) reported using fentanyl test strips (FTS) the last time they used DCS; 66% did so less than once per month. In the last six months, respondents used FTS to check methamphetamine (48%), heroin (30%) or fentanyl (29%). Relative to White/non-Latinx PWID, those who were non-White/Latinx were significantly less likely to have used DCS [adjusted risk ratio (aRR): 0.22; 95% CI: 0.10, 0.47), as were PWID experiencing homelessness (aRR:0.45; 95% CI: 0.28, 0.72). However, a significant interaction indicated that non-White/Latinx syringe service program (SSP) clients were more likely to have used DCS than non-SSP clients (aRR: 2.79; CI: 1.09, 7.2). Among all PWID, 44% expressed interest in free access to FTS, while 84% (of 196 PWID) expressed interest in advanced spectrometry DCS to identify and quantify multiple substances.

CONCLUSIONS

Our findings highlight low rates of DCS awareness and utilization, inequities by race/ethnicity and housing situation, high interest in advanced spectrometry DCS versus FTS, and the potential role of SSPs in improving access to DCS, especially among racial/ethnic minorities.

Water, Sanitation, and Hygiene (WaSH) insecurity in unhoused communities of Los Angeles, California

BACKGROUND

Access to water and sanitation is a basic human right; however, in many parts of the world, communities experience water, sanitation, and hygiene (WaSH) insecurity. While WaSH insecurity is prevalent in many low and middle-income countries, it is also a problem in high-income countries, like the United States, as is evident in vulnerable populations, including people experiencing homelessness. Limited knowledge exists about the coping strategies unhoused people use to access WaSH services. This study, therefore, examines WaSH access among unhoused communities in Los Angeles, California, a city with the second-highest count of unhoused people across the nation.

METHODS

We conducted a cross-sectional study using a snowball sampling technique with 263 unhoused people living in Skid Row, Los Angeles. We calculated frequencies and used multivariable models to describe (1) how unhoused communities cope and gain access to WaSH services in different places, and (2) what individual-level factors contribute to unhoused people's ability to access WaSH services.

RESULTS

Our findings reveal that access to WaSH services for unhoused communities in Los Angeles is most difficult at night. Reduced access to overnight sanitation resulted in 19% of the sample population using buckets inside their tents and 28% openly defecating in public spaces. Bottled water and public taps are the primary drinking water source, but 6% of the sample reported obtaining water from fire hydrants, and 50% of the population stores water for night use. Unhoused people also had limited access to water and soap for hand hygiene throughout the day, with 17% of the sample relying on hand sanitizer to clean their hands. Shower and laundry access were among the most limited services available, and reduced people's ability to maintain body hygiene practices and limited employment opportunities. Our regression models suggest that WaSH access is not homogenous among the unhoused. Community differences exist; the odds of having difficulty accessing sanitation services is two times greater for those living outside of Skid Row (Adj OR: 2.52; 95% CI: 1.08-6.37) and three times greater for people who have been unhoused for more than six years compared to people who have been unhoused for less than a year (Adj OR: 3.26; 95% CI: 1.36-8.07).

CONCLUSION

Overall, this study suggests a need for more permanent, 24-h access to WaSH services for unhoused communities living in Skid Row, including toilets, drinking water, water and soap for hand hygiene, showers, and laundry services.

Fentanyl, Heroin, and Methamphetamine-Based Counterfeit Pills Sold at Tourist-Oriented Pharmacies in Mexico: An Ethnographic and Drug Checking Study

Background

Our ethnographic team has conducted longitudinal research focused on illicit drug markets in Northern Mexico since 2018. In 2021-2022, study participants described the arrival of new, unusually potent tablets sold as ostensibly controlled substances, without a prescription, directly from pharmacies that cater to US tourists. Concurrently, fentanyl- and methamphetamine-based counterfeit prescription drugs have driven escalating overdose death rates in the US, however their presence in Mexico has not been assessed.

Aims

To characterize the availability of counterfeit and authentic controlled substances at pharmacies in Northern Mexico available to English-speaking tourists without a prescription.

Methods

We employed an iterative, exploratory, mixed methods design. Longitudinal ethnographic data was used to characterize tourist-oriented micro-neighborhoods and guide the selection of n=40 pharmacies in n=4 cities in Northern Mexico. In each pharmacy, samples of "oxycodone", "Xanax", and "Adderall" were sought as single pills, during English-language encounters, after which detailed ethnographic accounts were recorded. We employed immunoassay-based testing strips to check each pill for the presence of fentanyls, benzodiazepines, amphetamines, and methamphetamines. We used Fourier-Transform Infrared Spectroscopy to further characterize drug contents.

Results

Of 40 pharmacies, these controlled substances could be obtained in any form with no prescription at 68.3% and as single pills at 46.3%. Counterfeit pills were obtained at n=11 (26.8%) of pharmacies. Of n=45 samples sold as one-off controlled substances, n=20 were counterfeit including 9 of 11 (81.8%) of samples sold as "Adderall" that contained methamphetamine, and 8 of 27 (29.6%) of samples sold as "Oxycodone" that contained fentanyl, and n=3 'Oxycodone' samples containing heroin. Pharmacies providing counterfeit drugs were uniformly located in tourist-serving micro-neighborhoods, and generally featured English-language advertisements for erectile dysfunction medications and 'painkillers'. Pharmacy employees occasionally expressed concern about overdose risk and provided harm reduction guidance.

Discussion

The availability of fentanyl-, heroin-, and methamphetamine-based counterfeit medications in Northern Mexico represents a public health risk, and occurs in the context of 1) the normalization of medical tourism as a response to rising unaffordability of healthcare in the US, 2) plummeting rates of opioid prescription in the US, affecting both chronic pain patients and the availability of legitimate pharmaceuticals on the unregulated market, 3) the rise of fentanyl-based counterfeit opioids as a key driver of the fourth, and deadliest-to-date, wave of the opioid crisis. It is not possible to distinguish counterfeit medications based on appearance, because identically-appearing authentic and counterfeit versions are often sold in close geographic proximity. Nevertheless, US tourist drug consumers may be more trusting of controlled substances purchased directly from pharmacies. Due to Mexico's limited opioid overdose surveillance infrastructure, the current death rate from these substances remains unknown.

Correlates of recent overdose among people who inject drugs in the San Diego/Tijuana border region

BACKGROUND

Along the Mexico-US border, illicitly manufactured fentanyls (fentanyl) have been detected in other illicit drugs, including street opioid formulations known as 'china white.' We studied correlates of recent overdose among people who inject drugs (PWID), focusing on the risk of knowlingly or unknowingly using fentanyl in china white.

METHODS

From October 2020 - September, 2021 we surveyed participants in San Diego, California and Tijuana, Mexico and employed Poisson regression to identify correlates of recent overdose.

RESULTS

Of 612 PWID, most were male (74.0 %), Latinx (71.9 %), US residents (67.0 %). Mean age was 43 years. In the last six months, 15.8 % experienced overdose, 31.0 % knowingly used fentanyl and 11.1 % used china white, of whom 77.9 % did not think it contained fentanyl. After controlling for sex and race, factors independently associated with risk of overdose included knowingly using fentanyl, using china white and not believing it contained fentanyl, recent drug rehabilitation, being stopped/arrested by police, and homelessness. Further, PWID who believed china white contained fentanyl were less likely to use it.

CONCLUSIONS

Both intentional fentanyl use and unintentional exposure to fentanyl via china white were associated with overdose risk; however, PWID who believed china white contained fentanyl were less likely to use it. These data suggest that advanced drug checking systems should be implemented to empower PWID to avoid dangerous street formulations or to plan their drug use knowing its contents. Other overdose risk factors such as decreased tolerance following drug treatment, police interactions, and homelessness also require urgent intervention.