Ahimsa Porter Sumchai MD
14 min readMar 18, 2021


“In San Francisco’s Hunters Point 25,000 people live near a decommissioned naval base, including a 46-acre toxic waste dump and the remainders of the Navy’s radiological defense laboratory. According to some, it is one of the most polluted sites in the world, possibly for a long time to come. Is the Navy fulfilling its responsibility to the residents…or simply laying waste and walking off?” Saul Bloom — Shame About The Shipyard: The History of Environmental Contamination and Management of the Hunters Point Shipyard. Verdict — National Coalition of Concerned Legal Professionals — Vol. 8 №1 January 2002

Shame About The Shipyard by Saul Bloom- Verdict-April 2002 Illustration: Elizabeth Brizzi

Brain cancers are rare…the chance that you will be diagnosed with brain cancer in your lifetime is 0.6% based on 2017 data. The number of brain cancers diagnosed each year in the US is only 6 cases per 100,000. In stark contrast there are 125 cases of breast cancer and 120 cases of prostate cancer diagnosed annually for every 100,000 people.

The statistical odds are immeasurably low that in a community of 35,000 people multiple cases of brain cancer could be detected… yet Bayview Hunters Point residents often comment in community meetings and public hearings about friends, neighbors, relatives, pets and children who have been diagnosed with brain cancer!

Even more astounding is the fact the Hunters Point Community Biomonitoring Programs has identified multiple shipyard neighbors diagnosed with multiple brain tumors and have undergone urinary screenings that detect a toxic body burden of radioactive biomarkers and cancer causing heavy metals.

San Francisco Doctor Researches Impact of Toxic Dump on Hunters Point

HP Biomonitoring has evidence a rare cancer of the glial cells of the human brain called a brainstem glioma-proven to be induced by prolonged exposure to ionizing radiation and heavy metals- has been detected in Hunters Point residents and workers.

The environmental science, environmental justice and public health consequences of detecting a cluster of rare brain cancers in a neighborhood located within a one mile radius of three EPA designated federal Superfund sites are enormous!

Disparities in cancer incidences in Bayview Hunters Point residents were first documented in 1995 when a cluster of breast cancers was discovered by health department researchers. Between 1988 and 1992, 60 African American women were diagnosed with breast cancer - 41% were under the age of 50.

A 2000–2001 graph documents all cancers to be the third highest cause of excess deaths in BVHP and the second cause of years of life lost per death. DPH stopped publishing cancer data by zip code by 2009.

SFDPH 2004 Community Health Assessment documents 1280 total years of expected life lost due to all cancers placing ranking cancer above cerebrovascular disease for total years of expected life lost and second only to violence for average years of life lost per death.

A 2019 review of breast cancer disparities analyzed in Cancer Epidemiology, Biomarkers and Prevention found that while African American women comprised only 7.2% of breast cancer diagnoses in San Francisco from 2006 to 2015, in Bayview Hunters Point Black women represent 25.5% of breast cancer diagnoses and had the worst 5 year survival.

The findings starkly contradict the conclusions of Tomas Aragon, MD, DrPh — San Francisco’s former Health Officer- in a March 6, 2019 letter to Mayor London Breed. Aragon analyzed the same data as the independent scientists and concluded “no excess cancers of any type was seen in women” in BVHP.

Another one bites the dust! Tomas Aragon MD, DrPh, obviously frustrated by the demands of his job as the cities chief Health Officer and Director of Population Health, accepted Gavin Newsom’s appointment as director of the California Department of Public Health.

In a 1998 analysis of cancer in Bayview Hunters Point, Aragon explained the incidence of cancers detected in southeast San Francisco was so high it negatively affected cancer statistics for the entire City & County. Therefore, DPH stopped collecting cancer data by zip code and relied instead on data collected by the Greater Bay Area Cancer Registry. The strategic use of a bay area wide data registry served to statistically “dilute” the high cancer rates being detected in the 94124 zip code.

Alice: If you drink too much from a bottle marked “poison”, it’s almost certain to disagree with you sooner or later.

The San Francisco Department of Public Health released morbidity and mortality rates on the incidence of cancer, infectious diseases and injuries by zip code when I was a UCSF medical student during the 1980 AIDs era.

By 2009 DPH no longer published cancer incidences by zip code. Many believe it was due to unfolding events at the Hunters Point Shipyard where a 2010 Superior Court Civil Grand Jury report documented email collusion between health department officials, EPA regulators and environmental consultants for the shipyards master developer, Lennar.

Additionally, in 2009 the Navy disbanded the shipyards boisterous Restoration Advisory Board while DPH expanded Article 31 of the Health Code- allowing the Health Director to bill Lennar for oversight of “earthmoving” activities on the federal Superfund site to include the entire 500 acre base. Article 31 turned the Environmental Division of the Department of Public Health into a revenue generating enterprise department for the City & County of San Francisco.

“Cha-Ching” goes the cash register at the San Francisco Department of Public Health every time a backhoe excavator digs up a bucket load of contaminated dirt at the Hunters Point Shipyard under Article 31 of the Health Code adopted with the Parcel A transfer in 2004 and expanded to include the entire base in 2010 after the Navy disbanded the RAB. This photo captured by Hunters Point hilltop residents in June of 2020 captures a backhoe excavator at an unfortified fence line separating the federal Superfunds most contaminated regions from a dense residential neighborhood. On the other side of this fence is the Hunters Point Boys and Girls Club, Head Start and Muhammad University of Islam.
“Cha-Ching” goes the cash register at the San Francisco Department of Public Health as Amy Brownell, PE sells homes for Lennar Developers. Brownell is reimbursed via Article 31 of the Health Code for oversight of “earth moving” activities at a federal Superfund site.

The Navy decision to disband the RAB was opposed by the EPA. The Navy took action because RAB members failed to review cleanup documents, called for a Parcel A moratorium and unanimously supported a Civil Grand Jury Investigation that confirmed the conflict of interest between the Health Department and Lennar.

Additionally the Navy references twice the January 2009 unanimous vote to unseat Amy Brownell, PE as DPH Environmental Regulator after emails obtained via FOIA documented Brownell’s collusion to shut down a community air monitor -HV12- that registered astronomical exceedances in asbestos on a daily basis- along with a dialogue between Mark Ripperda of the EPA and a Lennar environmental consultant to “minimize shut down days” and the health impacts of toxic dust exposures generated by the grading of the Parcel A hilltop.

The Department of the Navy Base Realignment and Closure Program is in the process of reviewing the petition to reinstate the Hunters Point Shipyard RAB according to high level inside sources. The Navy makes valid complaints in identifying RAB members lack of review of documents.

In a letter dated March 2019 to San Francisco Mayor London Breed, Tomas Aragon, MD, DrPH examined cancer incidence for 12 types of cancers linked to radiation exposure and found a 31% increase in lung cancer in men living in 94124 for the years 2008–2012.

The list of 12 cancers Aragon analyzed excluded a major group of cancers widely accepted to be caused by radiation exposure…cancers of head, neck and brain!

MRI image of a child with a brainstem glioma. The SF Bayview front page features the photo of a Treasure Island child dying of this unrelenting cancer known to be caused by exposure to radiation and heavy metals.

Cancers of the head, neck, brain, breast and respiratory system are also cancers linked to air borne exposure to toxic pollutants according to World Trade Center Health Program entry guidelines. Thus, the decision by San Francisco’s population health officer to omit these cancers from the Bayview Hunters Point cancer review would likely have been deliberate.

Front page photo SF Bayview Newspaper by Carol Harvey 02/25/21 — “The Johnsons’ son, only 10 years old, is diagnosed with a brain stem glioma his mother believes is from exposure to toxins on Treasure Island.”
Cancer Incidence Among Residents of the Bayview-Hunters Point Neighborhood, San Francisco, California, 94124–2008–2012
San Francisco Police Officers were repeatedly assured by the San Francisco Department of Public Health that Building 606 was safe. Lead and petroleum products had been detected in drinking water and air monitoring once detected alarmingly high levels of toxic dust. Building 606 was built on the radioactive footprint of a laundry. Officers were exposed to radioactive soils dumped in three screening yards adjacent to the building.

I believe the exclusion of brain cancers from the DPH 2019 analysis of cancers in Bayview Hunters Point was deliberate because by 2018 a front page Chronicle investigation of San Francisco Police Officers stationed at Building 606 on the Hunters Point shipyard had identified two officers who underwent neurosurgery and/or died from brain cancer.

SFDPH was in the legal crosshair of a high powered law group representing 400 officers by 2019 and detecting excess brain cancers linked to radiation exposure at the Hunters Point shipyard opened the Health Department to public embarrassment, disrepute and a “deep pocket” legal recovery for criminal negligence in a wrongful death class action suit.

Tony Montoya was the 51 years old President of the Police Officers Association in 2018 when interviewed by San Francisco Chronicle journalists investigating Building 606 located on the southeast shoreline of the Hunters Point Naval Shipyard. Montoya was a K9 officer at Hunters Point from 2005–2008. Eight years later he developed a brain tumor that required emergency neurosurgical decompression. The Chronicle investigation did not identify the type of brain cancer Montoya had but his surgical scar is revealing. The posterior approach via the back of the neck and skull is used by neurosurgeons to excise brainstem gliomas.
A brainstem glioma is a cancerous brain tumor diagnosed most often in children and young adults. It is also diagnosed in adults over the age of 65 in what is called a bi-modal distribution. A glioma is made of glial cells. Glial cells are not neurons in the brains information network. New evidence links glia to pain perception. Glial cells form a spider web like supporting network throughout the brain. Many glials cells are called astrocytes because they look like stars. New research shows glial cells perform important functions and assist in processing memories, promote brain development, act to prevent infection as agents of the immune system and even “talk” to nearby neurons!
Pathways of Exposure: Unsuspecting children in a playground located in the 900 block of Palou at the Crisp Road entry to the Hunters Point Naval Shipyard’s chemical and radiation contaminated Parcel E-2 shoreline and industrial landfill. The fence line separating this dense residential neighborhood from the most dangerous region on the base is naked and not fortified with barriers to prevent gamma emitting fugitive dust particles from bombarding the fence line community.

She was as tall, smart and strong as any boy her age while growing up in the South Basin region of the Hunters Point shipyard. After college she began work as a physical therapist and started to “roll her ankle” over and over again. On medical evaluation problems with how she walked and how well she could balance herself were noted and an MRI scan was ordered. It showed a rare tumor at the base of her brain called a brainstem glioma.

Everything started to move real fast in her life after that brain scan! Over the next weeks she received thirty rounds of radiation treatments that caused her brain to swell. Her weakness and imbalance worsened after radiation but over time she regained her strength and moved on with her life.

The diffuse red area in the region at the base of the brain is a brainstem glioma in a little girl. Over 90% of children die within 2 years of this diagnosis according to Lancet Oncology
Think of the pink cortex of the brain as a flower bouquet and the brainstem as the stem. The brainstem is the more narrow tubular area at the base of the brain that regulates life control centers for breathing, heart rate, blood pressure control and movement.

But she wondered why — out of all the people around her — she was afflicted with brain cancer! She was fit and healthy and ate a healthy diet - that is until stress at work, nibbling, long hours and sleepless nights caused her to gained weight. She remembers growing up near Yosemite Slough — a muddy channel of water that runs west towards 3rd Street into the residential neighborhood where she spent her tom boy girlhood.

She grew up on the street next to a greasy muddy channel of water that drains from the dangerously contaminated Hunters Point shipyard southern shoreline and accumulates along with pollution from over a dozen nearby industries at Yosemite Slough. The EPA sued multiple major parties to secure funding for the clean up and restoration of Yosemite Slough. This photo was taken in 2020 by the author. Yosemite Slough is not being restored and is the site of chronic illegal dumping.

In 2016 the EPA sued the Navy, the City & County of San Francisco and over a dozen private polluting industries to secure funds for the clean-up and restoration of Yosemite Slough and in so doing designated it a federal Superfund site — the third in a one mile square region.

Yosemite Slough was once a spacious marine based ecosystem home to wildlife and multiple species of plants and animals. After years of toxic industrial waste, trash and debris generated by the runoff of the shipyards chemical and radiation contaminated shoreline and industrial landfill, lead, arsenic, pcbs and petroleum products were detected in a “stew” of contaminated mud.

Like a spider web is a magnified image of the glial cells in your brain that were once believed to act like scaffolding to support the neurons engaged in brain processing. Glial cells are as abundant as neurons and new evidence shows they play a role in pain perception, immune system regulation and in memory processing.

She underwent biomonitoring evaluation and urinary screening in 2020 driven by lingering questions about the cause of her brainstem glioma and smoldering concerns she was being exposed to toxic chemicals. The urinary screenings was remarkable for a young, fit and otherwise healthy woman. She had accumulated an enormous body burden of toxic chemicals that included Group 1 cancer causing heavy metals.

Nickel was detected in high concentrations along with cadmium — one of the most dangerous heavy metals. Toxic levels of aluminum, copper, iron, molybdenum, manganese, vanadium and chromium were also detected:

Genova Diagnostics Comprehensive Urine Elements Profile Screening conducted voluntarily on Hunters Point resident since early childhood diagnosed and treated for brainstem glioma. The urinary toxicology screening detects multiple cancer causing heavy metals and radioactive biomarkers in toxic range

Almost all heavy metals cause cancer when present in toxic concentrations but arsenic, cadmium, chromium and nickel are classified as group 1 carcinogens by the International Agency for Research on Cancer. Heavy metals used in industrials areas increase the opportunity for heavy exposure due to environmental contamination and accumulation in the human body. Heavy metals are found in batteries, paint and pigments used in children’s toys, jewelry and in vehicle emissions.

Astrocytomas are star shaped glial cells in the human brain. Glial cells can turn into cancerous gliomas when exposed to heavy metals commonly detected in the environment. Prolonged exposure to arsenic, nickel, lead, cadmium, chromium and mercury have been linked to brain cancer.

In 2002, 130 scientists from sixteen countries met at the Conference on Metal Toxicity and Carcinogenesis to present research on metal induced cancers. Heavy metals had been proven to alter genes in human and animal studies. Researchers analyzed data to better understand how heavy metals cause toxicity and cancer. They found heavy metals induce “oxidative stress, DNA damage and cell death processes resulting in an increased risk of cancer and cancer-related diseases.”

Gliomas arise as a result of genetic changes in glial cells. Several research studies document an increase in glioma incidence in people with prolonged exposure to heavy metals — specifically lead, nickel, chromium and cadmium. Brainstem gliomas are also linked to ionizing radiation exposure.

Brainstem gliomas are even more rare in adults and comprise only 1–2% of all intracranial gliomas. While research shows the incidence of brain cancer is higher among whites, African Americans diagnosed with brain cancer face a 13% increased risk of death due to surgical outcomes.

Alice: If you drink much from a bottle marked poison it is certain to disagree with you sooner or later.
“On November 7, 2000 some 287,000 San Franciscans sent a clear and unmistakable message to the federal government and the United States Navy: 87% of San Francisco voters passed Proposition P, a landmark initiative where for the first time in the history of the Superfund Program, the public determined the standard of cleanup.” Saul Bloom — Shame About The Shipyard: The History of Environmental Contamination and Management of the Hunters Point Shipyard. Vol 8, No 1 January 2002

I followed Saul Bloom down the enormous “rabbit hole” that remains of him in the historical archives of the Hunters Point Shipyard and discovered the connection between heavy metal exposure and gliomas. Bloom was 62 years old when he died of a malignant glioma in 2016. He was loved and hated… recognized and respected as founding Director of ARC/Ecology in San Francisco, where he agitated for environmental, ecological, economic and social justice.

Bloom will be remembered as the principal author of Proposition P — a voter led initiative on the November 7, 2000 municipal ballot in which 287,000 San Francisco voters said yes to the nations first community acceptance action codifying cleanup at a federal Superfund site. Proposition P called for cleanup of the Hunters Point Shipyard to residential standards — the highest standard called for under the federal Superfund Act.

Alice in Wonderland at the Hunters Point Shipyard: Image by former elected member of the shipyard RAB and artist Lani Ascher.

Bloom is singularly credited for shepherding the EPA designation of Yosemite Slough as a federal Superfund site. Arc Ecology was slated to lead the remediation and restoration of the Slough in 2016 when Bloom died, “in the loving arms of friends and family” of a malignant glioma no doubt induced by decades of exposure to radiation and heavy metals he publicly documents having been in contact with beginning in 1995 working alongside Astoria Metals at Hunters Point shipyard Dry Dock 4.

“Yesterday my brother, Saul Bloom, passed away. He died as a result of a 2 year long battle with brain cancer…he lost. I wonder if anybody actually wins this battle, regardless of length of survival it is a bitch of a disease and leaves only a trail of hurt…I loved and hated Saul, which is appropriate for brothers of the blood. He had the ability to make me see red with just a look. He was a huge force in shaping me to be who I am. I will miss him more than I can fathom. “

Saul Bloom offers medical documentation and legal proof of his exposure to radiation and heavy metals at the Hunters Point Shipyard in Verdict, Vol 8 April 2002. In 1995 the Navy agreed to lease Dry Dock #4 to the San Francisco Redevelopment Agency and Arc Ecology for a project designed to bring ship recycling opportunities to laid off shipyard workers. Arc Ecology conducted an environmental compliance verification that revealed, “the dry dock was a source of both metal and chemical contamination and the failure of the Navy to provide San Francisco with a correct report on the status and leasibility showed the project was off to a bad start and that there was much to be worried about.” Saul Bloom was right…there was much to be worried about!

The Hunters Point Community Biomonitoring Program has conducted urinary toxicology screenings on residents who have been diagnosed with multiple tumors and cancers arising in the brain including a Minister with a tumor of the pituitary gland diagnosed with an inoperable brainstem glioma.

The Minister has never met a neighbor who lives two blocks away. She has been a Hunters Point homeowner for 20 years and in 2020 she spoke courageously to the mainstream media after HP Biomonitoring conducted a urinary screening that revealed an enormous body burden of radioactive biomarkers and heavy metals in astounding concentrations that included cesium, gadolinium, nickel, rubidium, thallium, strontium, manganese and vanadium. Additionally, chromium, copper, zinc and magnesium were detected in elevated levels.

Urinary toxicology screening detects multiple toxic and radioactive elements in the red zones exceeding normal levels.

She walks her dog along the boundary of the shipyards radiation contaminated shoreline less than 500 feet from her house and served as an elected member of the Hunters Point Shipyard Restoration Advisory Board until the Navy disbanded it in 2009. She worked overnight shifts for the San Francisco Chronicle until disabled by chronic pain and multiple cancer and tumor diagnoses. She underwent surgery for breast cancer followed by neurosurgery -twice- to excise tumors compressing her brain. An ENT doctor examined her and obtained an MRI scan that showed tumors growing out of the auditory nerve in both ears.

Living in a south basin home about six blocks from her is a neighbor she has never met. She is a physically commanding professional woman with a doctorate in education who serves as a high ranking administrator for the San Francisco Unified School district. She has owned two homes in Hunters Point. In 1983 she was living in a modern development on the Hunters Point hilltop when she began experiencing symptoms of chronic asthma and underwent excision of a pulmonary nodule in her lung.

That same year she was diagnosed with a pituitary tumor in her brain and underwent neurosurgery performed by Charles Wilson, MD — Founding Chair of the internationally acclaimed UCSF Department of Neurological Surgery. I was her admitting intern in 1983.

Two years ago she developed problems with balance and an ENT doctor examined her and obtained an MRI scan that showed tumors growing out of the nerves of both ears… just like her Hunters Point neighbor who lives next door to the minister who was diagnosed with a pituitary tumor!

HP Biomonitoring conducted a urinary screening that detected arsenic in in toxic concentrations. Arsenic has been classified as a class 1 carcinogen by the International Agency of Research on Cancer and is associated with multiple tumors.

Gadolinium, cooper, manganese and rubidium are also detected in potentially toxic concentrations. High levels of thallium — a radioactive element so dangerous it was banned as a rat killer- are also detected.

Urinary toxicology screening detects alarming levels of arsenic above toxic range along with gadolinium, rubidium, copper, manganese and high levels of thallium.

Pathways of Exposure at the Hunters Point Shipyard

Window On The Shipyard — Dr. Ahimsa Sumchai and the Hunters Point Shipyard — Up Close and Personal! https://youtu.be/HwSOp6AgPuU

To understand how toxins documented to be present at a federal Superfund system accumulate over time in the human body let’s take a look at several important graphs:

The EPA Conceptual model depicts various pathways of exposure of known toxins to sensitive receptors in the environment including families with small children and the ecosystem. The findings of a consistent profile of shipyard soil elements in multiple urinary screenings conducted on residents and workers within its one mile perimeter can be best explained by airborne transmission. Indeed, HP Biomonitoring screened a Hunters Point hilltop resident during an asthma attack triggered by dust she sees in her environment and detected numerous soil elements in her urine corresponding to Parcel A soils.

Many of the soil elements detected in urinary screenings conducted by the Hunters Point Community Biomonitoring Program are derived from the serpentinite bedrock of the Hunters Point hilltop that has been graded for years creating a community wide exposure independent of age, gender, race and ethnicity in shipyard workers and neighbors. All are documented by the Navy and the EPA to be chemicals or radionuclides of concern at the federal Superfund site.

“Cha-Ching” goes the cash register at the San Francisco Department of Public Health as Lennar builds housing on the Hunters Point hilltop at the fenceline of a federal Superfund site.
An asthma attack in Hunters Point. Urinary toxicology screening conducted on hilltop resident with history of asthma triggered by dust she sees in her external environment detects numerous soil elements and carcinogenic metals including high levels of cadmium, cesium, nickel, rubidium, thallium, tungsten, copper, lithium, manganese, vanadium, zinc and potassium.
All of the elements detected on urinary toxicology screening of a Hunters Point hilltop resident during an asthma attack triggered by dust she sees in her external environment are chemicals of concern at the shipyard or are documented by the NRDL as radionuclides used in its experimentation.
“Cha-Ching” goes the cast register at the San Francisco Department of Public Helath as millions of tons of serpentinite rock has been graded from the Hunters Point hilltop for Lennar corporations residential development on Parcel A. New excavations began in the summer of 2020 during the worst wild fire season in US history and during the peak of the COVID-19 pandemic by executive order of Mayor London Breed.

The the original pre-clean EPA Hazard Ranking Score for the Treasure Island Naval Station — Hunters Point Annex predicted an 80% likelihood sensitive receptors nearby would be exposed to hazards at the federal Superfund site and a 100% probability sensitive receptors would be exposed by groundwater migration. Thus, the EPA predicted with 100% certainty that in January of 2019, when the Hunters Point Community Biomonitoring Program launched we would detect toxins from one EPA designated federal Superfund site…we have spawned to a system of three Superfund sites in 2021.

The federal Superfund system at the Hunters Point Naval Shipyard is the second most contaminated property on the National Priorities List with an overall ranking of 80 out of 100 and a 100% risk of hazard from groundwater migration.
“Cha-Ching” goes the cash register at the San Francisco Department of Public Health as deep soil excavations are conducted at the fenceline of a dense residential neighborhood adjacent to the federal Superfund site at the Hunters Point shipyard.
Geospatial mapping of radioactive biomarkers detected in high normal to floridly toxic concentrations in shipyard residents and workers. A cluster of six radionuclides of concern are concentrated along the historic main entry at Palou east to the radiation contaminated Parcel E-2 shoreline.
Unprotected shipyard worker exposed to piles of loose contaminated soil at a federal Superfund site.
Nursery school located in the 1000 block of Oakdale Avenue north of the Hunters Point Shipyard main entry at Crisp & Palou. Children are within 500 feet of the chemical and radiation contaminated Parcel E-2 shoreline and industrial landfill — a second federal Superfund site!
“Cha-Ching” goes the cash register at the San Francisco Department of Public Health as a backhoe excavator digs up buckets of radiation contaminated soil along the Parcel E-2 shoreline. A “naked” unfortified fence line separates the residential neighborhood to the north and west from gamma radiation documented to be present in Parcel E-2 soils.
As founding chair of the Radiological Subcommittee of the Hunters Point Shipyard Restoration Advisory Board I contributed to finalization of the Historical Radiological Assessment and advocated for Navy operations to remove the radiation contaminated storm drain systems throughout the base. In addition I served as a physician specialist for the Department of Public Health and established a children’s clinics in the Sunnydale housing projects…where I grew up. In 1997 I was attending physician for the Palo Alto VAH Toxic Registry and have served voluntarily as Health & Environmental Science Editor of the SF Bayview newspaper. I contributed to the Wikipedia editing of the Hunters Point Shipyard Gantry Crane.
In 1982 I became the first African American woman to train in neurological surgery in the University of California system having been accepted to both UCSF & UC San Diego.
Ahimsa Porter Sumchai MD

Founder, Director, PI - HP Biomonitoring/ Founding Chair- Radiological Committee Hunters Point Shipyard RAB 2001, Former Attending MD VA Toxic Registry & SFDPH