Local farmers who living within Nakornnayok sub-watershed daily used river waters for their household consumption, irrigations rice paddock, horticulture and aquaculture.  Those waters were abstracted and supplied through interconnected irrigation canals while the water flows controlled by many mechanical gates.  Wastewater discharged from cities, landfills, factories and others all flowed into those irrigated canals where accumulated much pollution and therefore often occurred at the riverbed downstream especially at Ban Na district and its surrounding neighbors.  Such pollution became intense since 1997 onwards, while the locals requested a helping hand from the provincial but such authority seemed rather had a limited capacity to deal with that problem.  The locals hence still widely faced critical health hazards, particularly with skin diseases when contacted with those polluted waters, while moreover the river waters could not be longer used for daily consumption.  The “perish green water” was commonly the so-called by many locals as the major cause of that  detrimental health hazards.  The locals eventually requested the Health Systems Research Institute researchers to explore any opportunities to alleviate such that problem. The research team agreed to apply the planned participatory action research type introducing to this case, while encouraged the locals to actively participate at every step of research implementation activities.  The study was conducted during January-June 2003.  The research framework was then logically organized focusing on building local learning process to exploring existing problems, rationalizing cause and effects of the problem encountered and eventually collectively finding the resolution measures.  The research activities eventually chronologically outlined were (1) exploring the scope of health impacts temporally and spatially using local health database, (2) selecting the highest health hazard prevalence within communities using focus group and in-depth interview techniques as to fine tune the impacts at individuals, family and community levels, (3) building local capacities on examination techniques on water pollution testing and its origin exploration, (4) using a mapping technique to associate water pollution occurrence and health impacts emerged, (5) organizing a local meeting to verify a study reported on fact findings, and (6) hosting the stakeholders meeting aimed to deliver the study results, and let the local representatives presented and proposed the mitigation measures, as expected to achieve a consensus agreement locally proposed to the provincial authorities to further develop policy and plan for pollution abatement.	This action research result eventually led to positive policy changed impact while the Nakornnayok provincial authority admitted to revise its environmental plan while much focused on resolving water pollution at the first priority.  The former activities listed in the environmental plan therefore has been changed and redirected in response to the local needs.  Further, the provincial also requested the municipalities, factories, irrigation authorities and sub-district administrations to revise their environmental related plan, and resubmitted to the provincial board.  The overall study result implied that the health impact assessment used by this study could be acted as a tool to further create local healthy public policy.  The learning process introduced by this study also proved to be an critical driving force, however such condition the locals still needed any organizations to helps them to develop success healthy public policy which originated from the grassroots.