PHI programs help farmworkers eat more healthily in California’s Central Valley, girls gain access to education in Nigeria, and hospitals support healthier populations across the US.

PHI’s comprehensive operational infrastructure allows us to quickly and effectively initiate new projects, serve as a fiscal sponsor, incubate new directions, partner with foundations and state agencies, and build collaborations across sectors.


Together, we are building a healthier world.

Learn more about our leadership below, or visit for an extensive overview of the programs and principal investigators that are a part of the PHI family, and to find out about our program impacts.

About PHI


Mary A. Pittman, DrPH

President & CEO

​A nationally recognized leader in improving community health, addressing health inequities among vulnerable people and promoting quality of care, Pittman assumed the reins at PHI in 2008, becoming the organization’s second president and CEO since its founding in 1964. Her primary focus has been guiding the development of a strategic plan that builds on existing PHI program strengths to achieve greater impact on public policy and practice in public health. “In a changing environment, strategic planning is an ongoing process, not an end product,” she said. Pittman’s overarching goal is for PHI to become known for leadership in creating healthier communities. She advocates that all PHI projects take the social determinants of health into account to better address health disparities and inequities. Under Pittman’s leadership, PHI has emphasized the integration of new technologies, creating, the online platform for conferencing and social networking that aims to build communities of interest for health. Other top priorities are: increasing advocacy for public policy and health reform, addressing health workforce shortages and the impacts of climate change on public health, and recognition of PHI as a preferred place to work. “I passionately believe that public health is an important component of health reform and has to have a stronger voice at the table,” Pittman said. She strives for PHI’s independent investigators to work together to achieve a synergy in which the sum of their contributions is greater than the whole.

Pittman has deep, varied and multi-sectoral experience in local public health, research, education and hospitals. Before joining PHI, Pittman headed the Health Research and Educational Trust, a Chicago-based affiliate of the American Hospital Association, from 1993 to 2007. Previously, she was president and CEO of the California Association of Public Hospitals and a director of the San Francisco Department of Public Health. Pittman has authored numerous peer-reviewed articles in scientific journals and two books. She has served on the PHI board of directors since 1996. Pittman also serves on numerous boards and committees, including the World Health Organization’s Health Worker Migration Global Policy Advisory Council and the National Patient Safety Foundation’s board of governors.

Mélange Matthews

Chief of Staff

Chief of staff and chief operating officer Mélange Matthews brings a wealth of expertise in management, planning, organizational support and policy analysis to PHI. Matthews is focused in part on ensuring PHI’s operational excellence and internal efficiency. “A strong internal foundation is vital to PHI’s success as a leading public health research, policy and advocacy organization,” Matthews said. With over two decades of public health experience, Matthews has served as the director and board chair of a number of local and statewide organizations. Matthews’ previous roles include acting director and chief operating officer for the San Francisco Mayor’s Office of Community Development, senior legislative planner for the San Francisco Department of Public Health; board member of the Regional Poison Control Center and member of the California Senate Medicaid Blue Ribbon Committee. As a consultant, Matthews has provided strategic planning and organizational support to foundations and nonprofits nationally. She has also taught critical theory and contemporary health issues at San Francisco State University. Matthews holds the degrees of Master of Public Health and Master of City and Regional Planning from the University of California at Berkeley.

Jim Simpson, JD, MPH

Chief General Counsel

​Simpson is responsible for a wide variety of legal and regulatory matters at PHI. He advises the president and CEO and the other members of the management team on major transactions, relationships with other institutions, policy development and new business initiatives. He also serves as PHI’s compliance officer and assistant secretary of the corporation. “Our legal department takes its cue from the public health approach: The best problem is one that doesn't happen,” Simpson said. “The best solution is simple and quick.” He has more than 20 years of experience advising nonprofit organizations. A member of the State Bar of California, Simpson received his law degree from the University of California at Berkeley and his master’s degree in public health from the University of California at Los Angeles.

Carmen R. Nevarez, MD, MPH

Vice President for External Affairs and Preventive Medicine Advisor

​A long-standing voice for the public's health, Nevarez is responsible at PHI for developing relationships with health and public health organizations and interests, incubating new project areas and public health advocacy. She is the director of PHI's Center for Health Leadership and Practice. She served as president of the American Public Health Association in 2010. At PHI, Nevarez positions the organization for further partnerships and initiatives domestically and internationally. She is the creator of, a web-based conferencing center that uses Web Forums, a social network and other resources to encourage collaboration between the prevention community and those communities whose work impacts health.  Her areas of expertise include teenage pregnancy prevention, health disparities, Latino health, obesity, and chronic disease prevention and health reform. Before coming to PHI, Nevarez served as the director, health officer and environmental health director for Berkeley's Health and Human Services Department, after which she worked as a special assistant to the dean at the University of California, Berkeley, School of Public Health, developing university participation in community-based public health projects and teaching a graduate course in multicultural competence. She has served as medical director at La Clinica de la Raza in Oakland, a federally qualified health center. A gynecologist and preventive medicine specialist, Nevarez maintains a part-time clinical practice.

Tamar Dorfman, MPP

Chief Financial Officer

Chief Financial Officer Tamar Dorfman leads the Public Health Institute's finance & accounting, grants & contracts, and audit & compliance teams. For more than a decade she has directed finance and operations in non-profit and public sector organizations that promote community development, workforce development, and affordable housing. Her career has focused on developing strong financial strategies and efficient operations so that organizations can maximize impact while ensuring compliance with funder and regulatory requirements. Prior to joining PHI, Dorfman was the Chief Financial Officer for PolicyLink, and the Mayor's Offices of Community Investment and Housing in San Francisco. She also served as the Fiscal Manager for the Corporation for Supportive Housing and was a Principal Budget Analyst for the City of Chicago. She holds a Masters in Public Policy from the University of Chicago and a Bachelor's degree from Stanford University.

Matthew Marsom

Vice President of Public Policy and Programs

As PHI’s vice president for public policy and programs, Marsom is responsible for monitoring and influencing public health policy, legislation and regulations that affect PHI projects and interests. “This role is about moving strategically and acting as a voice for PHI on state, federal and global public policy issues that support our larger mission,” Marsom said. “Given the changes in Washington, this is an opportune and exciting time to enhance our role.” Marsom positions PHI to cultivate understanding and support for public health, primarily at the state legislative and administrative levels, but also as appropriate with Congress, federal agencies and community organizations. Previously, he was chief of the Policy, Partnerships and Planning Unit of the Cancer Prevention and Nutrition Section of the California Department of Public Health, providing support for policy development, legislative analysis and external relations. He also oversaw the policy and partnership activities of the Network for a Healthy California. Marsom, originally from the United Kingdom, was an advocate for community-based child care organizations and an advisor for policy and strategy within the Early Years and Childcare Unit for the Department of Education and Skills in London. He received his bachelor’s degree with First-Class Honors in political science from the University of Stirling in Scotland and postgraduate certificates in Russian and research methods from the University of Glasgow in Scotland.

Valerie McCann Woodson

Vice President of Human Resources

​Valerie McCann Woodson, vice president of human resources, has responsibility for attracting and supporting PHI employees. She leads the Human Resources and Office Services teams who are specifically responsible for talent management acquisition, compensation, payroll, benefits, HR information system, employee relations, performance management and professional development. She is delighted that PHI provides benefits and programs that continue to drive employee engagement upward and has resulted in PHI being selected as a “Best Place to Work.” As one of many who recognize that PHI’s employees truly are our best asset, she focuses on developing and implementing policy and services that are meaningful and valued by staff at all levels of the organization. Valerie began her professional career as chemical engineer at Procter and Gamble in Cincinnati Ohio with responsibility for product and technology development. Her additional roles included those of corporate recruiter and diversity trainer. Valerie was pleased to serve as the P&G company representative for the Howard University Cluster where she served as a member of the Executive Board. She holds a B.S. in Chemical Engineering from Howard University School of Engineering. She joined the Public Health Institute in 1996.

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PHI has twice been named among the

TOP 50 nonprofits

to work for

by the nonprofit times


Anthony A. Barrueta, JD,

Senior Vice President of Government Relations

Kaiser Foundation Health Plan

Oakland, California

Debbie Chang

Senior Vice President, Policy and Prevention

Nemours Children’s Health System

Washington, DC 

Denise Dunning, PhD


Rise Up, Public Health Institute

Oakland, California

Nick Macchione, FACHE

Agency Director and Deputy Chief Administrative Officer

County of San Diego Health and Human Services Agency

San Diego, California 

Mary A. Pittman, DrPH

President & Chief Executive Officer

Public Health Institute

Oakland, California

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Dara Johnson Treseder, MBA, Secretary/Treasurer

Chief Marketing Officer, Carbon

Co-Founder and Former CEO, NeuBridges
Sunnyvale, California

Susan Dentzer

Visiting Fellow

The Duke-Margolis Center for Health Policy
Cambridge, Massachusetts

Adaeze Enekwechi, PhD, MPP



Washington, DC

Andrew Pines, MBA

Retired Managing Director
Orinda, California

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