The Controversy Surrounding 6-PPD and 6-PPD-quinone_2

Overall Structure of the Forum

Themes include
・6PPD
・6PPD-quinone
・Tire wear-derived chemicals
・Fish toxicity
・Urban stormwater measures

The format centers on lightning talks.
Research, standard design, and implementation technologies proceed simultaneously.

Not merely an academic conference,
but closer to a pre-stage of institutional formation.

The Issue of 6PPD-quinone

Formed through oxidation of 6PPD contained in tires.

Characteristics
・Acute toxicity to Coho salmon at extremely low concentrations
・Detected in urban runoff
・Correlation with traffic volume

The issue lies in the concentration level.

・EPA screening value 11 ng/L
・State standard 12 ng/L

Reanalysis of existing acute toxicity data shows
・Average mortality 2–3%
・Up to about 15% mortality possible at the upper confidence interval

“Protection of 95% of species”
and “complete protection of a specific endangered population” are based on different design philosophies.

Standard values are institutional values rather than scientific values.

Premises of Analytical Technology

EPA Draft Method 1634.

Automation of solid phase extraction (SPE).

・Recovery rate approx. 90%
・Reproducibility approx. 2%

Standardization of measurement
is the basis for policy decisions.

What cannot be measured cannot be regulated.

What Is Bioretention

A system that treats urban stormwater
using soil, microorganisms, and plants.

Structure
・Vegetation layer
・Amended soil layer
・Adsorption layer
・Drainage layer

Treatment mechanisms
・Physical filtration
・Adsorption
・Microbial degradation
・Plant uptake

For 6PPDQ
・Removal rate over 98%
・Cases below detection limit
・Zero acute mortality (experimental conditions)

Implementation stage has already begun.

Alternative and Complementary Technologies

Other solutions where constraints exist.

・Floating treatment modules
・Small devices for bridge drainage outlets
・Porous pavement
・Regional treatment facilities for high-traffic roads

Common feature
Based on existing infrastructure.

Not full reconstruction
but additional systems.

Cold Region Conditions

Observed examples
・Tendency for concentration increase in winter
・Use of deicing agents
・Hypothesis of increased winter tire wear

Seasonal variation is an important condition in institutional design.

Discussion cannot rely on annual averages.

Priority Design

State Departments of Transportation integrate
・Traffic volume
・Salmon recovery plans
・Environmental justice
・Tribal interests

into GIS to extract priority sections.

Scientific data
is converted into an investment map.

Institutional Conditions

The technology exists.

Remaining issues include
・Definition of acceptable concentration
・Consistency with endangered species protection
・Cost allocation
・Urban structural constraints
・Maintenance systems

Interface between science and institutions.

Personal Notes

・6PPDQ is an ultra-low concentration problem
・Pollution dependent on urban transportation
・Treatment technology is high performance
・Standards include value judgments