Analytical Methodology¶
Follow the Money¶
Port Health Watch follows a "follow the money" methodology — tracing financial flows through public health systems to reveal the hidden costs that port-adjacent communities bear from shipping emissions. Every tonne of PM2.5 emitted at berth generates a quantifiable health burden — premature deaths, hospitalizations, emergency department visits, lost work days — that can be monetized using EPA's own valuation framework.
This methodology does not create new science. It applies the same concentration-response functions and monetization methods that EPA uses in its own Regulatory Impact Analyses for Clean Air Act standards — to the specific context of port communities that currently lack this analysis.
Analytical Framework¶
Four principles govern every Port Health Watch assessment:
1. Data Triangulation¶
No single data source is trusted in isolation. Each finding is cross-referenced across multiple independent sources:
| Data Category | Primary Source | Cross-Reference Sources |
|---|---|---|
| Emissions | ICCT goPEIT | EPA NEI, state air permits, AIS vessel tracking |
| Air quality | EPA AirNow/AQS | MPCA monitoring, WI DNR reports |
| Health outcomes | CDC PLACES | State health dept surveillance, county CHNA, hospital discharge data |
| Demographics | Census ACS | EJScreen, SVI, local planning documents |
| Compliance | EPA ECHO | State enforcement databases, FOIA returns |
When sources disagree, the discrepancy is documented and the most conservative (lowest impact) estimate is used as the primary figure, with the range reported.
2. Temporal Alignment¶
All data inputs are time-aligned to the same reporting period where possible. The Duluth-Superior assessment uses:
- Baseline year: 2022 (matching the Port Authority's Climate Action Plan)
- Current period: 2025 (most recent available data)
- Projection horizon: 2026–2030 (including MERC closure impact)
Where data vintages differ (e.g., Census ACS 5-year estimates vs. annual EPA monitoring), the temporal mismatch is documented and its potential impact on results is noted.
3. Spatial Resolution¶
All analysis is conducted at the census tract level — the finest resolution at which health, demographic, and environmental data are simultaneously available. This enables:
- Identification of specific neighborhoods bearing disproportionate impact
- Environmental justice analysis at the community level
- Spatial correlation between emission sources and health outcomes
- Mapping of cumulative exposure from multiple sources (port + rail + industrial)
Three analysis radii are used for the Duluth-Superior assessment:
| Radius | Population | Purpose |
|---|---|---|
| 1 mile | ~15,000 | Immediate port-adjacent impact zone |
| 3 miles | ~92,000 | Primary health impact assessment boundary |
| 5 miles | ~115,000 | Extended metro area and regional context |
4. Regulatory Context Mapping¶
Each data finding is mapped against the regulatory framework that governs it — identifying which agency has jurisdiction, what standards apply, and where enforcement gaps exist. This transforms raw data into actionable intelligence for advocacy, grant applications, and regulatory proceedings.
Health Impact Methodology¶
Concentration-Response Functions¶
Health impacts are quantified using the EPA's BenMAP-CE framework with peer-reviewed concentration-response functions:
| Health Endpoint | Source Study | Effect Estimate |
|---|---|---|
| All-cause mortality (adults 30+) | Krewski et al. 2009 (ACS CPS-II) | 6% increase per 10 µg/m³ PM2.5 |
| Cardiovascular hospitalizations | Zanobetti et al. 2009 (Medicare cohort) | Cohort-derived estimates |
| Respiratory hospitalizations | Zanobetti et al. 2009 | Cohort-derived estimates |
| Asthma ED visits | Mar et al. 2010 (multi-city study) | Multi-city derived estimates |
The primary mortality function (Krewski et al. 2009) is the lower-bound estimate. The Lepeule et al. 2012 extended follow-up (14% per 10 µg/m³) would produce higher impact estimates but is used as a sensitivity analysis, not the primary figure.
Monetization¶
| Value | Amount | Source |
|---|---|---|
| Value of Statistical Life (VSL) | $11.8 million | EPA (2024-adjusted) |
| Cardiovascular hospitalization | $56,000 | EPA cost-of-illness |
| Respiratory hospitalization | $42,000 | EPA cost-of-illness |
| Asthma ED visit | $850 | EPA willingness-to-pay |
| Lost work day | $200 | BLS average daily wage |
Conservatism¶
All estimates in this assessment are conservative by design:
- Uses lower-bound Krewski (2009) CRF, not higher Lepeule (2012)
- Excludes secondary PM2.5 formation from NOx and SOx (would increase totals)
- Excludes chronic morbidity endpoints (cancer, neurological effects) despite strong evidence
- Uses dispersion modeling screening estimates, not site-specific modeling (which would provide higher spatial resolution)
- Reports ranges reflecting uncertainty rather than single-point estimates
Quality Assurance Standards¶
Provenance Documentation¶
Every data point in the assessment traces to a named source with publication date, access method, and retrieval date. No data is used without provenance.
Raw Data Preservation¶
All downloaded datasets, API responses, and FOIA returns are archived in their original format. Analysis scripts operate on copies, preserving the raw record.
Replication-Ready Methodology¶
All calculations use documented formulas with published coefficients. Any researcher with access to the same public data sources can replicate the findings using the methodology documented here and in the site-wide methodology page.
Peer Review Alignment¶
The health impact quantification methodology mirrors the approach used in:
- EPA Regulatory Impact Analyses for NAAQS
- ICCT port emissions screening methodology
- Academic health impact assessment literature (Anenberg et al., Fann et al., Goodkind et al.)
This alignment ensures that findings are defensible in regulatory proceedings, grant applications, and academic peer review.
Civil Ledger Lab Platform¶
Port Health Watch is a research initiative of EcoAsset Lab LLC, operating as part of the Civil Ledger Lab platform. The Civil Ledger Lab applies forensic-grade public records analysis to environmental and public health questions — following financial flows, regulatory filings, and compliance data to quantify the costs that communities bear from industrial pollution.
The methodology described here is one application of the broader Civil Ledger Lab analytical framework, adapted specifically for port community health impact assessment.
Last updated: April 2026
Methodology references: EPA BenMAP-CE, Krewski et al. 2009 (ACS CPS-II), Zanobetti et al. 2009, Mar et al. 2010, EPA VSL Guidance (2024), ICCT goPEIT Technical Documentation