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Air Quality Health Units (AQHUs)

A Proposed Framework for Quantifying Port Health Benefits

Key Concept

1 AQHU = 1 Disability-Adjusted Life Year (DALY) avoided through verified reduction in port-attributable air pollution exposure.

The Problem

Carbon credit methodologies quantify greenhouse gas reductions. They do not capture the health co-benefits of emissions reduction — even when those health benefits are orders of magnitude larger than the carbon value.

At a port, a barge-mounted capture system that removes 99% of PM2.5 and 95% of NOx simultaneously prevents premature deaths, hospitalizations, and asthma attacks in surrounding communities. These health benefits are real, measurable, and monetizable — but they currently have no market mechanism.

Verra's SD VISta program currently has only one approved asset methodology (time savings from cookstoves). No methodology exists for air quality health benefits from any source, let alone port emissions. This is an open field.

The Framework

Air Quality Health Units (AQHUs) are being developed for submission to Verra's SD VISta program, which certifies Sustainable Development contributions aligned with the UN Sustainable Development Goals. AQHUs are designed to be complementary to, not duplicative of, carbon credits — they quantify health co-benefits that Verified Carbon Units (VCUs) do not capture.

Quantification Process

Step 1 — Measure: Emissions captured per vessel-hour using verified monitoring data from the capture system. PM2.5 and NOx mass removed, independently measured.

Step 2 — Model: Concentration reduction in surrounding communities using EPA-standard dispersion modeling (InMAP or BenMAP). Two approaches supported:

  • Approach A (Preferred): Site-specific dispersion modeling using monitored emissions data and local meteorology
  • Approach B (Screening): Transfer coefficients from ICCT goPEIT screening data, calibrated with EPA InMAP reduced-complexity modeling

Step 3 — Quantify: Translate concentration reductions into avoided DALYs using:

  • Peer-reviewed concentration-response functions (Krewski et al. 2009; Lepeule et al. 2012)
  • WHO disability weight tables for PM2.5-attributable disease endpoints
  • Local baseline health outcome rates from state/county health departments
  • Exposed population counts from U.S. Census at census tract resolution

Step 4 — Verify: Independent third-party validation of each step, producing verified AQHUs eligible for registration under SD VISta.

SDG Alignment

AQHUs directly support three UN Sustainable Development Goals:

  • SDG 3 (Good Health and Well-Being): Quantified reduction in premature mortality and respiratory disease
  • SDG 10 (Reduced Inequalities): Health benefits concentrated in low-income communities and communities of color bearing disproportionate pollution burden
  • SDG 11 (Sustainable Cities and Communities): Measurably cleaner air in urban port neighborhoods

Why This Matters for Communities

For port-adjacent communities, AQHUs represent something new: a financial mechanism that directly values their health. Currently, the health costs of port pollution are externalities — borne by communities, invisible in the economics of shipping. AQHUs internalize those costs by creating a market for their avoidance.

A port authority or shipping company deploying at-berth capture generates AQHUs proportional to the health benefit delivered to surrounding communities. This creates a direct financial link between investment in emissions control and the health outcomes of the people who breathe the air.

Open Questions

Several methodological challenges remain to be resolved before submission. We are documenting them openly because the answers will determine whether AQHUs are credible as a tradable asset class.

DALY valuation. Published DALY valuations span a wide range ($500–$5,000 per avoided DALY in the literature), driven by differences in methodology (cost-of-illness vs. willingness-to-pay vs. VSL-derived), geographic scope, and whose baseline health burden is used. An AQHU valuation standard needs a defensible anchor — most likely EPA's Value of a Statistical Life applied to attributable mortality, with morbidity endpoints valued separately.

Verification standards for dispersion modeling. InMAP and BenMAP are accepted in U.S. regulatory contexts, but Verra has no precedent for accepting reduced-complexity dispersion modeling as a verification basis. Establishing the verification standard — what inputs must be measured vs. modeled, what tolerances apply, what independent verifier credentials are required — is a prerequisite for methodology accreditation.

Attribution in multi-source environments. Port-adjacent communities are exposed to PM2.5 and NOx from many sources (port vessels, drayage trucks, rail, refineries, background urban sources). Attributing specific health outcomes to specific capture operations requires a robust apportionment method. The closer the capture source is to a monitored receptor, the cleaner the attribution — but general rules need to be established.

Program structure fit. SD VISta was designed to label co-benefits of existing VCS projects, not to certify a new asset class on its own. Whether SD VISta's current program structure can accommodate AQHUs as a standalone instrument, or whether a new program structure is required, is a question we are working through with Verra.

Empirical validation. The MERC coal terminal closure at the Port of Duluth-Superior (June 30, 2026) provides the first natural experiment for AQHU methodology validation — a clean before/after baseline for measuring port-attributable PM2.5 reductions and the corresponding health benefits. This is the first opportunity to stress-test the quantification chain against observed rather than modeled concentration changes.

Status

The AQHU framework is currently in concept development, with formal submission to Verra's SD VISta program targeted for 2026. The concept note draws on the health impact quantification methodology detailed in our Methodology section and demonstrated in our NY/NJ port assessment and Duluth-Superior assessment.

For research collaboration, early access to the concept framework, or community partnership inquiries, contact us.