An Urgent Need for Evidence-Based Guidance on Mercury Exposure Screening to Inform Public Health Policy,Practice,and Prevention

Study Design and Approach

We conducted a qualitative study using semistructured interviews to examine primary care clinicians’ knowledge, practices, perceived barriers, and facilitators related to mercury exposure screening and risk assessment among socioeconomically vulnerable populations in New York City. A qualitative approach was appropriate given the exploratory nature of the topic, limited guidance on mercury screening in primary care, and the aim to generate in-depth practice-informed insights within a clinically relevant urban context where multiple exposure pathways may occur. Reporting followed the consolidated criteria for reporting qualitative research. ⁴⁰ The University of New Haven Institutional Review Board reviewed and approved this study (2025-013), and the research team conducted all procedures in accordance with institutional ethical standards.

Research Team and Reflexivity

The study’s lead investigator (N.B.), a doctoral researcher trained in qualitative methods with experience in public health practice and research, conducted all interviews. Participants had no prior professional relationship with the interviewer. The interviewer aimed to minimize assumptions during data collection and analysis and documented analytic decisions to support reflexivity and transparency. To strengthen interpretive rigor, the interviewer iteratively discussed theme development and interpretation with a senior researcher (P.R.) during the study to ensure that findings were grounded in participant accounts.

Participants and Recruitment

Participants were primary care clinicians, including physicians, nurse practitioners, and physician assistants, who provide direct patient care to New York City residents. We used purposive sampling to recruit clinicians from outpatient clinics and hospital-affiliated settings serving racially, ethnically, and socioeconomically diverse and vulnerable populations. We distributed interview invitations via email and text through professional contacts, and we encouraged participants to share the invitation with colleagues, using a snowball sampling approach. Recruitment continued until we achieved thematic saturation, resulting in 12 completed interviews from April through June 2025.

Data Collection

We conducted the interviews with clinicians online via Microsoft Teams or by telephone, with each interview lasting approximately 15 to 30 minutes. Before participation, clinicians received a study information sheet describing the purpose, procedures, and confidentiality protections, and we obtained written informed consent. We also obtained and documented verbal informed consent before each interview in accordance with institutional review board–approved procedures. We audio-recorded the interviews with permission and transcribed them verbatim. The interview guide included questions designed to examine clinicians’ knowledge and training related to mercury exposure, screening and risk assessment practices, barriers and facilitators to routine identification, and recommendations for practical tools or guidance. The Knowledge-to-Action framework guided development of the interview guide and analytic focus to examine gaps in evidence, clinical practice, and implementation support systems.^38,39

Data Analysis

We analyzed transcripts using reflexive thematic analysis following Braun and Clarke’s 6-phase approach. ⁴¹ The research team read transcripts repeatedly for familiarization and generated initial codes across the dataset. We then grouped codes into candidate themes aligned with study aims and reviewed and refined them for coherence across participants. We used structured Microsoft Excel–based matrixes to organize codes, themes, and illustrative quotes and to maintain an audit trail. Before analysis, we removed identifying information.

Participant Characteristics

Twelve primary care clinicians (P1-P12) participated: 6 physicians, 4 nurse practitioners, and 2 physician assistants (Table 1). Participants practiced across multiple outpatient settings in New York City, primarily in the Bronx and Queens. Six participants worked in hospital-based clinics and 6 in private family medicine practices. Most participants served racially and ethnically diverse, low-income, uninsured, and immigrant populations, many with limited English proficiency and limited access to preventive services.

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Table 1.

Characteristics, mercury exposure–related training, and guideline familiarity among 12 primary care clinicians participating in qualitative interviews conducted in New York City, April 2025

Participant ID	Health care provider type	Practice setting	NYC borough	Patient populations served	Mercury exposure–related training	Familiarity with mercury screening guidelines
P1	Physician	Hospital-based outpatient clinic	Bronx/Queens	Low-income, immigrant, family practice	Limited (brief mention in medical school)	Limited
P2	Physician	Hospital-based outpatient clinic	Bronx/Queens	Adult, oncology/complex care	Limited (brief toxicology exposure)	Limited
P3	Physician	Hospital-based setting	Bronx	Adult inpatient/acute care	Minimal (medical school only)	Minimal
P4	Physician	Private family practice	Queens	Mixed age, low income	Minimal	Minimal
P5	Physician	Private family practice	Bronx	Pediatric/family, immigrant	Minimal	Minimal
P6	Physician	Private practice	Queens	Mixed age, urban	Minimal	Minimal
P7	Nurse practitioner	Private family practice	Bronx	Pediatric/family, immigrant	Minimal (brief nurse practitioner program exposure)	Minimal
P8	Nurse practitioner	Hospital-affiliated outpatient clinic	Queens	Adult primary care	Minimal	Minimal
P9	Nurse practitioner	Private practice	Bronx	Adult, medically underserved	Minimal	Minimal
P10	Nurse practitioner	Private practice	Queens	Adult primary care	None reported	None
P11	Physician assistant	Hospital-based setting	Bronx	Pediatric and adult	Minimal (physician assistant school mention)	Minimal
P12	Physician assistant	Hospital-affiliated primary care	Bronx	Adult, uninsured, immigrant	None reported	None

Abbreviations: ID, identification; NYC, New York City.

Across roles and settings, clinicians reported minimal formal training related to mercury exposure or screening and limited familiarity with existing guidance. Key themes and illustrative quotes are summarized in Table 2.

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Table 2.

Key themes and illustrative quotes from qualitative interviews with 12 primary care clinicians regarding mercury exposure screening in New York City, April 2025

Theme	Summary of clinician perspectives on mercury screening	Illustrative quotes	Participants illustrating theme
Theme 1. Mercury exposure is not clinically salient in primary care	Mercury is recognized as toxic but perceived as peripheral, theoretical, or irrelevant to routine practice. Clinicians lack applied knowledge of exposure pathways, risk thresholds, and screening indications.	“I know mercury is toxic, but I couldn’t tell you the levels that are concerning or what symptoms to look for.” (P1) “I know mercury can come from eating certain fish . . . but I’ve never really seen a patient with mercury issues.” (P3)	P1, P3, P6, P9
Theme 2. Screening is rare, reactive, and largely symptom-driven	Mercury screening is not preventive or routine; testing occurs only in response to unusual symptoms or specific exposure histories.	“It would be filed as an incidental finding in the ER, not something we actively look for.” (P4) “If someone had unexplained tremors, then maybe I’d think about mercury.” (P3)	P3, P4, P5, P8
Theme 3. Structural and health care system–level barriers drive inconsistent practice	Lack of testing infrastructure, health insurance restrictions, time pressures, and unclear follow-up pathways discourage screening.	“I don’t know if we even have the order for mercury.” (P11) “You need a solid diagnosis or insurance denies it.” (P7)	P3, P7, P10, P11
Theme 4. Absence of institutional guidance and clinical decision support	Without protocols, EHR prompts, or standardized workflows, mercury screening depends on individual clinician judgment.	“There are protocols for lead but not mercury. That makes it feel like it’s not important.” (P7) “If the clinic had a protocol, I’d follow it.” (P2)	P2, P7, P9
Theme 5. Strong support for standardized, practical screening guidance	Clinicians favor evidence-based guidance modeled on lead or asthma screening, with clear thresholds and next steps.	“Having similar guidelines for mercury could help with identifying patients at high risk and what to do next.” (P2)	P2, P4, P6
Theme 6. Clinician-identified strategies for implementation and prevention	Health care providers recommend brief screening tools, EHR integration, team-based workflows, and public health engagement.	“Short risk questions could be asked at intake and flagged in the EMR.” (P9) “Guidelines need to be short and easy to interpret to save time.” (P12)	P1, P9, P12

Abbreviations: EHR, electronic health record; EMR, electronic medical record; ER, emergency room.

Theme 1: Mercury Exposure Is Not Clinically Salient in Primary Care

Clinicians consistently described mercury exposure as peripheral rather than integrated into routine care. While most recognized mercury as toxic, they lacked applied knowledge of exposure pathways, populations at risk of mercury exposure, screening thresholds, or follow-up steps. Awareness of mercury exposure pathways was typically limited to fish consumption or industrial exposure and was often attributed to media coverage or brief training references.

Some interviewees interpreted the absence of screening as a sign of limited clinical relevance. As a physician explained, “I know mercury can come from eating certain fish like tuna or swordfish, and maybe from industrial work, but I’ve never really seen a patient with mercury issues in my practice” (P3). In the absence of systematic screening or guidance, clinicians may have limited opportunities to identify mercury exposure even when it is present. Another interviewee noted, “We talk about lead exposure more often; mercury just doesn’t come up unless it’s in the news” (P6).

Several clinicians acknowledged uncertainty about how mercury exposure might present clinically or when screening would be appropriate, with one stating, “I know mercury is toxic, but I couldn’t tell you the levels that are concerning or what symptoms to look for” (P1). Participants also expressed uncertainty about the local epidemiology of mercury exposure. As one remarked, “I’m not sure how common this type of exposure is specifically in New York City” (P9).

Theme 2: Screening Is Rare, Reactive, and Largely Symptom-Driven

No participants described mercury screening as part of routine preventive care. Instead, clinicians described testing as rare and triggered by unusual symptoms or known exposures. Clinicians reported considering testing primarily in cases of unexplained neurologic symptoms, pediatric concerns, or occupational risk.

One clinician summarized, “Right now, we don’t have anything in place to do that . . . it’s not something we have on our radar” (P1). Another stated, “It would be filed as an incidental finding in the ER [emergency room], not something we actively look for” (P4).

When testing occurred, it was prompted by atypical presentations rather than systematic risk assessment. One interviewee said, “If someone had a weird metallic taste or unexplained tremors, then maybe I’d think about mercury” (P3). Another recalled, “I had a case where a child came from abroad and had both lead and mercury checked, but that was exceptional” (P5).

Theme 3: Structural and Health Care System–Level Barriers Drive Inconsistent Practice

Clinicians emphasized that limited screening reflected structural barriers rather than lack of concern. A central issue was uncertainty about testing infrastructure, including how to order tests and how to interpret results. One participant said, “I don’t know if we even have the order for mercury,” and later asked, “If you get the results and they end up being high, then what do you do next?” (P6).

Absence of health insurance coverage was another barrier to mercury testing. As a clinician explained, “You need to have a solid and valid diagnosis to test for mercury. If not, insurance denies it—that’s the biggest obstacle.” Time constraints further limited clinicians’ ability to assess environmental exposure risks.

Several clinicians described busy primary care workflows with limited opportunity to take detailed exposure histories. One participant stated, “It’s hard to take a full exposure history when you have 15 minutes per patient” (P3).

Theme 4: Absence of Institutional Guidance and Clinical Decision Support

Participants consistently contrasted mercury screening with lead screening, highlighting the absence of protocols, electronic health record prompts, and standardized workflows for mercury screening. One participant noted, “There are protocols for lead but not mercury. That makes it feel like it’s not important” (P7). Another clinician stated, “If the clinic had a protocol, I’d follow it. But without it, mercury just falls through the cracks” (P2).

The lack of electronic health record prompts and order sets further limited uptake. Clinicians reported relying on external resources such as UpToDate when confronted with unfamiliar exposures, underscoring the absence of integrated decision support.

Theme 5: Strong Support for Standardized, Practical Screening Guidance

Despite limited current screening, clinicians supported formal, evidence-based guidance. Several interviewees endorsed adapting models from lead, asthma, or depression screening. One participant stated, “Having similar guidelines for mercury could help with identifying patients at high risk and what to do next if levels are high” (P2). Other interviewees suggested incorporating mercury screening into annual visits or pairing it with lead protocols to improve efficiency.

Participants emphasized that guidelines would need to be accompanied by education. One noted, “Knowledge and awareness would be very helpful for pediatricians, OB/GYNs [obstetricians-gynecologists], and primary care providers” (P6).

Theme 6: Clinician-Identified Strategies for Implementation and Prevention

Participants offered concrete recommendations to operationalize mercury screening in primary care settings, including the development of brief risk-based questionnaires, digital screening tools or calculators, and integration of screening into intake or triage workflows. Several clinicians suggested that medical assistants could administer short screening tools, with automated prompts guiding health care providers when follow-up testing is indicated.

Clinicians also emphasized the importance of public health engagement to complement clinical screening. Suggested strategies included patient education materials, clinic posters, and broad public health communication campaigns to raise awareness of mercury exposure risks. Participants stressed that screening guidance should be concise, easy to interpret, and supported by clear referral pathways to make mercury screening as feasible and routine as lead testing.

Limitations

This study had several limitations. First, it included a qualitative sample of primary care clinicians from New York City, and findings may not be generalizable to other regions or health care systems. Second, data were based on self-reported clinician perspectives and may reflect recall bias or social desirability influences. Third, the study focused exclusively on clinician experiences and did not include patient perspectives, public health officials, or direct observation of clinical workflows, which may limit understanding of how barriers to mercury exposure screening are experienced and operationalized across the health care system and care settings. Fourth, the analysis addressed mercury exposure broadly and did not distinguish among specific exposure pathways or assess clinical outcomes. The aim was to identify gaps in screening infrastructure and implementation readiness rather than to evaluate the effectiveness of certain mercury screening approaches or interventions. However, thematic saturation was achieved, and the study was conducted in a setting with documented mercury exposure risks, supporting the relevance and transferability of the identified implementation gaps. Future research across diverse geographic contexts, including coastal, riverine, and industrial regions, can build on these findings to further inform screening strategies.