Reported xylazine exposure highly associated with overdose outcomes in a rapid community assessment among people who inject drugs in Baltimore.

BACKGROUND: Addressing xylazine harms are now a critical harm reduction priority, but relatively little epidemiological information exists to determine prevalence, magnitude, and correlates of xylazine use or related outcomes. METHODS: We conducted a rapid behavioral survey among people who inject drugs (n = 96) in Baltimore November-December 2022. Using a novel indicator of self-reported presumed xylazine effects, we examined prevalence and sociodemographic correlates of past year presumed xylazine effects and association with overdose and wound-related outcomes. Chi-square and descriptive statistics were used to examine bivariate associations overall and separately for those who reported xylazine by name and by reported fentanyl use frequency. RESULTS: Almost two-thirds (61.5%) reported experiencing xylazine effects. There were no differences by socio-demographics, but xylazine effects were more commonly reported among those who reported injecting alone (66% vs 38%%, p < 0.007) and daily fentanyl use (47% vs 24% p < 0.003). Those reporting xylazine exposure was three times as likely to report overdose (32% vs 11%, p < 0.03) and twice as likely to have used naloxone (78% vs 46%, p < 0.003). They also more commonly reported knowing someone who died of an overdose (92% vs 76%, p < 0.09) and to report an abscess requiring medical attention (36% vs 19%, p < 0.80). These associations were higher among respondents who specifically named xylazine and those who used fentanyl more frequently, but fentanyl frequency did not fully explain the heightened associations with xylazine effects. CONCLUSIONS: This study provides insight into the scope of xylazine exposure and associated health concerns among community-based PWID and suggests measures that may be instrumental for urgently needed research.

Injection Behaviors and Use of Syringe Service Programs over Time among People Who Inject Drugs in Baltimore, Maryland.

Introduction: People who inject drugs (PWID) are at increased risk for infectious disease transmission, including hepatitis C and HIV. Understanding trends in injection risk behaviors and syringe service program (SSP) use over time can help improve infectious disease prevention and other harm reduction services. Methods: Using National HIV Behavioral Surveillance System data from Baltimore, Maryland, we examined changes in receptive sharing of (1) syringes, (2) injection equipment, (3) syringes to divide drugs; and (4) receipt of syringes from SSPs among PWID from 2009 to 2018 (n = 518 in 2009, n = 638 in 2012, n = 586 in 2015, and n = 575 in 2018) using unadjusted and adjusted logistic models calculated across time for the total sample. Results: The conditional probability of receptive sharing of syringes and receipt of syringes from SSPs remained relatively stable, while receptive sharing of injection equipment and receptive sharing of syringes to divide drugs dropped substantially after 2009. White race and daily injection frequency were positively associated with sharing syringes and injection equipment and negatively associated with SSP use over time. In 2015, there was a notable shift such that women were twice as likely as men to receive syringes from SSPs and less likely than men to report the use of shared syringes or equipment. Conclusion: Findings indicate overall steady or decreasing trends in injection risk and steady trends in SSP usage over time, with some notable improvements among women and indications of shifting drug market patterns. Injection-related risk behaviors remain high among White PWID and may require targeted outreach and interventions.

RNA-Based Control of Fungal Pathogens in Plants.

Our duty to conserve global natural ecosystems is increasingly in conflict with our need to feed an expanding population. The use of conventional pesticides not only damages the environment and vulnerable biodiversity but can also still fail to prevent crop losses of 20-40% due to pests and pathogens. There is a growing call for more ecologically sustainable pathogen control measures. RNA-based biopesticides offer an eco-friendly alternative to the use of conventional fungicides for crop protection. The genetic modification (GM) of crops remains controversial in many countries, though expression of transgenes inducing pathogen-specific RNA interference (RNAi) has been proven effective against many agronomically important fungal pathogens. The topical application of pathogen-specific RNAi-inducing sprays is a more responsive, GM-free approach to conventional RNAi transgene-based crop protection. The specific targeting of essential pathogen genes, the development of RNAi-nanoparticle carrier spray formulations, and the possible structural modifications to the RNA molecules themselves are crucial to the success of this novel technology. Here, we outline the current understanding of gene silencing pathways in plants and fungi and summarize the pioneering and recent work exploring RNA-based biopesticides for crop protection against fungal pathogens, with a focus on spray-induced gene silencing (SIGS). Further, we discuss factors that could affect the success of RNA-based control strategies, including RNA uptake, stability, amplification, and movement within and between the plant host and pathogen, as well as the cost and design of RNA pesticides.

BioClay™ prolongs RNA interference-mediated crop protection against Botrytis cinerea.

One of the most promising tools for the control of fungal plant diseases is spray-induced gene silencing (SIGS). In SIGS, small interfering RNA (siRNA) or double-stranded RNA (dsRNA) targeting essential or virulence-related pathogen genes are exogenously applied to plants and postharvest products to trigger RNA interference (RNAi) of the targeted genes, inhibiting fungal growth and disease. However, SIGS is limited by the unstable nature of RNA under environmental conditions. The use of layered double hydroxide or clay particles as carriers to deliver biologically active dsRNA, a formulation termed BioClay™, can enhance RNA durability on plants, prolonging its activity against pathogens. Here, we demonstrate that dsRNA delivered as BioClay can prolong protection against Botrytis cinerea, a major plant fungal pathogen, on tomato leaves and fruit and on mature chickpea plants. BioClay increased the protection window from 1 to 3 weeks on tomato leaves and from 5 to 10 days on tomato fruits, when compared with naked dsRNA. In flowering chickpea plants, BioClay provided prolonged protection for up to 4 weeks, covering the critical period of poding, whereas naked dsRNA provided limited protection. This research represents a major step forward for the adoption of SIGS as an eco-friendly alternative to traditional fungicides.

Wellbeing and Aging in The Australian Women's Weekly magazine.

This study investigates how the wellbeing trend in popular media regulates women's bodies and their selves through establishing norms around successful aging. We report on an exploratory qualitative content analysis of representations of wellbeing and aging from The Australian Women's Weekly (AWW) magazine. While some articles emphasized self-care and self-responsibility, many articulated relational and social/structural understandings of wellbeing. Compared with an earlier analysis of the AWW, our study found largely positive views of experiences of aging, associated with new opportunities and increased self-acceptance. These findings demonstrate how magazines both reflect and reinforce subtle processes of social change.

Flavodiiron-Mediated O2 Photoreduction Links H2 Production with CO2 Fixation during the Anaerobic Induction of Photosynthesis.

Some microalgae, such as Chlamydomonas reinhardtii, harbor a highly flexible photosynthetic apparatus capable of using different electron acceptors, including carbon dioxide (CO2), protons, or oxygen (O2), allowing survival in diverse habitats. During anaerobic induction of photosynthesis, molecular O2 is produced at photosystem II, while at the photosystem I acceptor side, the reduction of protons into hydrogen (H2) by the plastidial [FeFe]-hydrogenases primes CO2 fixation. Although the interaction between H2 production and CO2 fixation has been studied extensively, their interplay with O2 produced by photosynthesis has not been considered. By simultaneously measuring gas exchange and chlorophyll fluorescence, we identified an O2 photoreduction mechanism that functions during anaerobic dark-to-light transitions and demonstrate that flavodiiron proteins (Flvs) are the major players involved in light-dependent O2 uptake. We further show that Flv-mediated O2 uptake is critical for the rapid induction of CO2 fixation but is not involved in the creation of the micro-oxic niches proposed previously to protect the [FeFe]-hydrogenase from O2 By studying a mutant lacking both hydrogenases (HYDA1 and HYDA2) and both Flvs (FLVA and FLVB), we show that the induction of photosynthesis is strongly delayed in the absence of both sets of proteins. Based on these data, we propose that Flvs are involved in an important intracellular O2 recycling process, which acts as a relay between H2 production and CO2 fixation.

Cultivar and phosphorus effects on switchgrass yield and rhizosphere microbial diversity.

Switchgrass (Panicum virgatum L.) is a native perennial grass identified as a promising biofuel crop for production on marginal agricultural lands. As such, research into switchgrass fertility and the switchgrass rhizosphere microbiome has been ongoing in an effort to increase production sustainability. We examined the effects of cultivar and phosphorus (P) fertilization on biomass yield, P removal, and rhizosphere bacterial and fungal community structure in three switchgrass cultivars: Sunburst, Shawnee, and Liberty. The Liberty cv. is the first lowland-type bioenergy switchgrass adapted to USDA hardiness zones 4, 5, and 6. On a medium soil test P clay loam soil, biomass yield response to applied P was linear, increasing 135 kg ha-1 for every kilogram of P applied prior to establishment. Average post-frost biomass yield was 9.6 Mg ha-1 year-1 when unfertilized, and maximum biomass yield was 10.3 Mg ha-1 year-1 when fertilized at 58.6 kg ha-1 P, suggesting that P application on medium soil test P soils is beneficial for switchgrass establishment and early growth. Switchgrass cv. Shawnee was more productive than cvs. Liberty or Sunburst (11.3, 10.2, and 8.6 Mg ha-1 year-1, respectively). Both bacterial and fungal communities were significantly shaped by cultivar. These shifts, while inconsistent between year and cultivar, may reflect a selection of the microbial community from that present in soil to maximize total nutrient uptake, regardless of additional P amendments. Phosphorus fertilization did not affect microbial community structure. Results of this study suggest that the cultivar-associated selection of particular microbial taxa may have implications for increased productivity.

Compartmentalisation of [FeFe]-hydrogenase maturation in Chlamydomonas reinhardtii.

Molecular hydrogen (H2 ) can be produced in green microalgae by [FeFe]-hydrogenases as a direct product of photosynthesis. The Chlamydomonas reinhardtii hydrogenase HYDA1 contains a catalytic site comprising a classic [4Fe4S] cluster linked to a unique 2Fe sub-cluster. From in vitro studies it appears that the [4Fe4S] cluster is incorporated first by the housekeeping FeS cluster assembly machinery, followed by the 2Fe sub-cluster, whose biosynthesis requires the specific maturases HYDEF and HYDG. To investigate the maturation process in vivo, we expressed HYDA1 from the C. reinhardtii chloroplast and nuclear genomes (with and without a chloroplast transit peptide) in a hydrogenase-deficient mutant strain, and examined the cellular enzymatic hydrogenase activity, as well as in vivo H2 production. The transformants expressing HYDA1 from the chloroplast genome displayed levels of H2 production comparable to the wild type, as did the transformants expressing full-length HYDA1 from the nuclear genome. In contrast, cells equipped with cytoplasm-targeted HYDA1 produced inactive enzyme, which could only be activated in vitro after reconstitution of the [4Fe4S] cluster. This indicates that the HYDA1 FeS cluster can only be built by the chloroplastic FeS cluster assembly machinery. Further, the expression of a bacterial hydrogenase gene, CPI, from the C. reinhardtii chloroplast genome resulted in H2 -producing strains, demonstrating that a hydrogenase with a very different structure can fulfil the role of HYDA1 in vivo and that overexpression of foreign hydrogenases in C. reinhardtii is possible. All chloroplast transformants were stable and no toxic effects were seen from HYDA1 or CPI expression.

Muscle MRI in patients with dysferlinopathy: pattern recognition and implications for clinical trials.

BACKGROUND AND OBJECTIVE: Dysferlinopathies are a group of muscle disorders caused by mutations in the DYSF gene. Previous muscle imaging studies describe a selective pattern of muscle involvement in smaller patient cohorts, but a large imaging study across the entire spectrum of the dysferlinopathies had not been performed and previous imaging findings were not correlated with functional tests. METHODS: We present cross-sectional T1-weighted muscle MRI data from 182 patients with genetically confirmed dysferlinopathies. We have analysed the pattern of muscles involved in the disease using hierarchical analysis and presented it as heatmaps. Results of the MRI scans have been correlated with relevant functional tests for each region of the body analysed. RESULTS: In 181 of the 182 patients scanned, we observed muscle pathology on T1-weighted images, with the gastrocnemius medialis and the soleus being the most commonly affected muscles. A similar pattern of involvement was identified in most patients regardless of their clinical presentation. Increased muscle pathology on MRI correlated positively with disease duration and functional impairment. CONCLUSIONS: The information generated by this study is of high diagnostic value and important for clinical trial development. We have been able to describe a pattern that can be considered as characteristic of dysferlinopathy. We have defined the natural history of the disease from a radiological point of view. These results enabled the identification of the most relevant regions of interest for quantitative MRI in longitudinal studies, such as clinical trials. CLINICAL TRIAL REGISTRATION: NCT01676077.

The structurally unique photosynthetic Chlorella variabilis NC64A hydrogenase does not interact with plant-type ferredoxins.

Hydrogenases from green algae are linked to the photosynthetic electron transfer chain via the plant-type ferredoxin PetF. In this work the [FeFe]-hydrogenase from the Trebouxiophycean alga Chlorella variabilis NC64A (CvHydA1), which in contrast to other green algal hydrogenases contains additional FeS-cluster binding domains, was purified and specific enzyme activities for both hydrogen (H2) production and H2 oxidation were determined. Interestingly, although C. variabilis NC64A, like many Chlorophycean algal strains, exhibited light-dependent H2 production activity upon sulfur deprivation, CvHydA1 did not interact in vitro with several plant-type [2Fe-2S]-ferredoxins, but only with a bacterial2[4Fe4S]-ferredoxin. In an electrochemical characterization, the enzyme exhibited features typical of bacterial [FeFe]-hydrogenases (e.g. minor anaerobic oxidative inactivation), as well as of algal enzymes (very high oxygen sensitivity).

Evolution of Chlamydomonas reinhardtii ferredoxins and their interactions with [FeFe]-hydrogenases.

Ferredoxins are soluble iron sulphur proteins which function as electron donors in a number of metabolic pathways in a broad range of organisms. In photosynthetic organisms, PETF, or ferredoxin 1 (FDX1), is the most studied ferredoxin due to its essential role in photosynthesis, where it transfers electrons from photosystem I to ferredoxin-NADP+ oxidoreductase. However, PETF can also transfer electrons to a large number of other proteins. One important PETF electron acceptor found in green microalgae is the biologically and biotechnologically important [FeFe]-hydrogenase HYDA, which catalyses the production of molecular hydrogen (H2) from protons and electrons. The interaction between PETF and HYDA is of considerable interest, as PETF is the primary electron donor to HYDA and electron supply is one of the main limiting factors for H2 production on a commercial scale. Although there is no three dimensional structure of the PETF-HYDA complex available, protein variants, nuclear magnetic resonance titration studies, molecular dynamics and modelling have provided considerable insight into the residues essential for forming and maintaining the interaction. In this review, we discuss the most recent findings with regard to ferredoxin-HYDA interactions and the evolution of the various Chlamydomonas reinhardtii ferredoxin isoforms. Finally, we provide an outlook on new PETF-based biotechnological approaches for improved H2 production efficiencies.

Acceptability of microbicidal vaginal rings and oral pre-exposure prophylaxis for HIV prevention among female sex workers in a high-prevalence US city.

Biomedical HIV prevention tools including oral pre-exposure prophylaxis (PrEP) and vaginal microbicidal rings hold unique value for high-risk women who may have limited capacity for condom negotiation, including the key populations of sex workers and drug users. Commercial sex is a PrEP indicator in CDC guidelines, yet little is known about female sex workers' (FSWs) knowledge of and attitudes toward PrEP or the recently developed monthly vaginal microbicide rings. We describe knowledge and attitudes toward PrEP and microbicide rings in a sample of 60 mostly drug-using FSWs in Baltimore, Maryland, a high HIV-prevalence US city. Just 33% had heard of PrEP, but 65% were interested in taking daily oral PrEP and 76% were interested in a microbicide vaginal ring; 87% were interested in at least one of the two methods. Results suggest method mix will be important as biomedical tools for HIV prophylaxis are implemented and scaled up in this population, as 12% were interested in PrEP but not vaginal rings, while 19% were interested in vaginal rings but not in PrEP. Self-efficacy for daily oral adherence was high (79%) and 78% were interested in using PrEP even if condoms were still necessary. Women who had experienced recent client-perpetrated violence were significantly more interested in PrEP (86% vs 53%, p = 0.009) and microbicidal rings (91% vs 65%, p = 0.028) than women who had not recently experienced violence. No differences were observed by demographics nor HIV risk behaviors, suggesting broad potential interest in daily PrEP and monthly-use vaginal microbicides in this high-risk population.

Occupational Safety in the Age of the Opioid Crisis: Needle Stick Injury among Baltimore Police.

At a time of resurgence in injection drug use and injection-attributable infections, needle stick injury (NSI) risk and its correlates among police remain understudied. In the context of occupational safety training, a convenience sample of 771 Baltimore city police officers responded to a self-administered survey. Domains included NSI experience, protective behaviors, and attitudes towards syringe exchange programs. Sixty officers (8%) reported lifetime NSI. Officers identifying as Latino or other race were almost three times more likely (aOR 2.58, 95% CI 1.12-5.96) to have experienced NSI compared to whites, after adjusting for potential confounders. Findings highlight disparate burdens of NSIs among officers of color, elevating risk of hepatitis, HIV, and trauma. Training, equipment, and other measures to improve occupational safety are critical to attracting and safeguarding police, especially minority officers.

A brief, trauma-informed intervention increases safety behavior and reduces HIV risk for drug-involved women who trade sex.

BACKGROUND: Female sex workers (FSWs) are an important population for HIV acquisition and transmission. Their risks are shaped by behavioral, sexual network, and structural level factors. Violence is pervasive and associated with HIV risk behavior and infection, yet interventions to address the dual epidemics of violence and HIV among FSWs are limited. METHODS: We used participatory methods to develop a brief, trauma-informed intervention, INSPIRE (Integrating Safety Promotion with HIV Risk Reduction), to improve safety and reduce HIV risk for FSWs. A quasi-experimental, single group pretest-posttest study evaluated intervention feasibility, acceptability and efficacy among FSWs in Baltimore, MD, most of whom were drug-involved (baseline n = 60; follow-up n = 39 [65%]; non-differential by demographics or outcomes). Qualitative data collected at follow-up contextualizes findings. RESULTS: Based on community partnership and FSW input, emergent goals included violence-related support, connection with services, and buffering against structural forces that blame FSWs for violence. Qualitative and quantitative results demonstrate feasibility and acceptability. At follow-up, improvements were seen in avoidance of client condom negotiation (p = 0.04), and frequency of sex trade under the influence of drugs or alcohol (p = 0.04). Women's safety behavior increased (p < 0.001). Participants improved knowledge and use of sexual violence support (p < 0.01) and use of intimate partner violence support (p < 0.01). By follow-up, most respondents (68.4%) knew at least one program to obtain assistance reporting violence to police. Over the short follow-up period, client violence increased. In reflecting on intervention acceptability, participants emphasized the value of a safe and supportive space to discuss violence. DISCUSSION: This brief, trauma-informed intervention was feasible and highly acceptable to FSWs. It prompted safety behavior, mitigated sex trade under the influence, and bolstered confidence in condom negotiation. INSPIRE influenced endpoints deemed valuable by community partners, specifically improving connection to support services and building confidence in the face of myths that falsely blame sex workers for violence. Violence persisted; prevention also requires targeting perpetrators, and longer follow-up durations as women acquire safety skills. This pilot study informs scalable interventions that address trauma and its impact on HIV acquisition and care trajectories for FSWs. CONCLUSION: Addressing violence in the context of HIV prevention is feasible, acceptable to FSWs, and can improve safety and reduce HIV risk, thus supporting FSW health and human rights.

Challenges and opportunities for hydrogen production from microalgae.

The global population is predicted to increase from ~7.3 billion to over 9 billion people by 2050. Together with rising economic growth, this is forecast to result in a 50% increase in fuel demand, which will have to be met while reducing carbon dioxide (CO2 ) emissions by 50-80% to maintain social, political, energy and climate security. This tension between rising fuel demand and the requirement for rapid global decarbonization highlights the need to fast-track the coordinated development and deployment of efficient cost-effective renewable technologies for the production of CO2 neutral energy. Currently, only 20% of global energy is provided as electricity, while 80% is provided as fuel. Hydrogen (H2 ) is the most advanced CO2 -free fuel and provides a 'common' energy currency as it can be produced via a range of renewable technologies, including photovoltaic (PV), wind, wave and biological systems such as microalgae, to power the next generation of H2 fuel cells. Microalgae production systems for carbon-based fuel (oil and ethanol) are now at the demonstration scale. This review focuses on evaluating the potential of microalgal technologies for the commercial production of solar-driven H2 from water. It summarizes key global technology drivers, the potential and theoretical limits of microalgal H2 production systems, emerging strategies to engineer next-generation systems and how these fit into an evolving H2 economy.

Solution structure of the RNA-binding cold-shock domain of the Chlamydomonas reinhardtii NAB1 protein and insights into RNA recognition.

Light-harvesting complex (LHC) proteins are among the most abundant proteins on Earth and play critical roles in photosynthesis, both in light capture and in photoprotective mechanisms. The Chlamydomonas reinhardtii nucleic acid-binding protein 1 (NAB1) is a negative regulator of LHC protein translation. Its N-terminal cold-shock domain (CSD) binds to a 13-nt element [CSD consensus sequence (CSDCS)] found in the mRNA of specific LHC proteins associated with Photosystem II (PSII), an interaction which regulates LHC expression and, consequently, PSII-associated antenna size, structure and function. In the present study, we elucidated the solution structure of the NAB1 CSD as determined by heteronuclear NMR. The CSD adopts a characteristic five-stranded anti parallel ß-barrel fold. Upon addition of CSDCS RNA, a large number of NMR chemical shift perturbations were observed, corresponding primarily to surface-exposed residues within the highly conserved ß2- and ß3-strands in the canonical RNA-binding region, but also to residues on ß-strand 5 extending the positive surface patch and the overall RNA-binding site. Additional chemical shift perturbations that accompanied RNA binding involved buried residues, suggesting that transcript recognition is accompanied by conformational change. Our results indicate that NAB1 associates with RNA transcripts through a mechanism involving its CSD that is conserved with mechanisms of sequence-specific nucleic acid recognition employed by ancestrally related bacterial cold-shock proteins (CSPs).

[FeFe]-Hydrogenase with Chalcogenide Substitutions at the H-Cluster Maintains Full H2 Evolution Activity.

The [FeFe]-hydrogenase HYDA1 from Chlamydomonas reinhardtii is particularly amenable to biochemical and biophysical characterization because the H-cluster in the active site is the only inorganic cofactor present. Herein, we present the complete chemical incorporation of the H-cluster into the HYDA1-apoprotein scaffold and, furthermore, the successful replacement of sulfur in the native [4FeH ] cluster with selenium. The crystal structure of the reconstituted pre-mature HYDA1[4Fe4Se]H protein was determined, and a catalytically intact artificial H-cluster variant was generated upon in vitro maturation. Full hydrogen evolution activity as well as native-like composition and behavior of the redesigned enzyme were verified through kinetic assays, FTIR spectroscopy, and X-ray structure analysis. These findings reveal that even a bioinorganic active site with exceptional complexity can exhibit a surprising level of compositional plasticity.

Sulphur responsiveness of the Chlamydomonas reinhardtii LHCBM9 promoter.

MAIN CONCLUSION: A 44-base-pair region in the Chlamydomonas reinhardtii LHCBM9 promoter is essential for sulphur responsiveness. The photosynthetic light-harvesting complex (LHC) proteins play essential roles both in light capture, the first step of photosynthesis, and in photoprotective mechanisms. In contrast to the other LHC proteins and the majority of photosynthesis proteins, the Chlamydomonas reinhardtii photosystem II-associated LHC protein, LHCBM9, was recently reported to be up-regulated under sulphur deprivation conditions, which also induce hydrogen production. Here, we examined the sulphur responsiveness of the LHCBM9 gene at the transcriptional level, through promoter deletion analysis. The LHCBM9 promoter was found to be responsive to sulphur deprivation, with a 44-base-pair region between nucleotide positions -136 and -180 relative to the translation start site identified as essential for this response. Anaerobiosis was found to enhance promoter activity under sulphur deprivation conditions, however, alone was unable to induce promoter activity. The study of LHCBM9 is of biological and biotechnological importance, as its expression is linked to photobiological hydrogen production, theoretically the most efficient process for biofuel production, while the simplicity of using an S-deprivation trigger enables the development of a novel C. reinhardtii-inducible promoter system based on LHCBM9.

MR system operator: recommended minimum requirements for performing MRI in human subjects in a research setting.

This article is intended to provide guidelines for the minimum level of safety and operational knowledge that an MR system operator should exhibit in order to safely perform an MR procedure in a human subject in a research setting. This article represents the position of the International Society for Magnetic Resonance in Medicine (ISMRM) regarding this important topic and was developed by members of this society's MR Safety Committee.

Police Encounters Among Needle Exchange Clients in Baltimore: Drug Law Enforcement as a Structural Determinant of Health.

OBJECTIVES: We piloted a monitoring mechanism to document police encounters around programs targeting people who inject drugs (PWID), and assessed their demographic predictors at 2 Baltimore, Maryland, needle exchange program (NEP) sites. METHODS: In a brief survey, 308 clients quantified, characterized, and sited recent police encounters. Multivariate linear regression determined encounter predictors, and we used geocoordinate maps to illustrate clusters. RESULTS: Within the past 6 months, clients reported a median of 3 stops near NEP sites (interquartile range [IQR] = 0-7.5) and a median of 1 arrest in any location (IQR = 0-2). Three respondents reported police referral to the NEP. Being younger (P = .009), being male (P = .033), and making frequent NEP visits (P = .02) were associated with reported police stops. Among clients reporting arrest or citation for syringe possession, Whites were significantly less likely than non-Whites to report being en route to or from an NEP (P < .001). Reported encounters were clustered around NEPs. CONCLUSIONS: Systematic surveillance of structural determinants of health for PWID proved feasible when integrated into service activities. Improved monitoring is critical to informing interventions to align policing with public health, especially among groups subject to disproportionate levels of drug law enforcement.