Health fears linger in a Brazilian neighborhood built over oil waste

SÃO SEBASTIÃO, Brazil — In front of the house where she has lived for decades, Cosma da Silva points to nearby homes in her Itatinga neighborhood and lists a string of cancer cases. “There’s a woman with cancer over there. Another one lives in that building. And yet another one there [points at the place]. People in this area only die of cancer.”

She sees illness as an integral part of the neighborhood’s landscape and includes her own family in the tally. Her husband Paulo José da Silva died at age 51 from a brain tumor. Cosma herself recently underwent surgery to remove a nodule. As she deals with the consequences of the treatment — a wound that burns and itches on the side of her chest — she continues to observe several sick relatives, neighbors and acquaintances.

The connection between these cases and the environmental contamination that has marked Itatinga’s history has never been proven or investigated the way residents expected it to be.

From the 1970s to the 1980s, part of the neighborhood was used for the disposal of oily sludge associated with oil exploration. Years later, homes were built on the land. Environmental investigations by public agencies found contaminants in the soil and groundwater.

For almost 20 years, documents from the São Paulo State Environmental Company (CETESB), the State Prosecution Service (MPE), the Federal Prosecution Service (MPF) and Petrobras itself — the Brazilian state-controlled oil company, which the investigations accused of being responsible for the disposal — pointed to toxic substances on the site. In technical reports, CETESB noted the presence of benzene and hydrocarbons in the ground, highlighting their carcinogenic risks.

Nevertheless, a main study intended to assess health impacts on the population has never been conducted.

A community built on sludge

Before the city expanded, the neighborhood’s area was occupied by small crops and bamboo groves. Residents say oil industry waste was deposited there for years until the land was filled, subdivided and sold as a result of urban expansion. Many families argue that they learned of that history long after settling in the area.

Maria do Carmo Barbosa da Silva has lived in the neighborhood for more than three decades. She recalls that when she arrived there used to be crops, livestock and a river for bathing, fishing and washing clothes. She says a dark substance began to appear in several areas of the community in the early 2000s. The sludge would turn out in backyards, sidewalks, streets and vacant lots. “It was a black sludge with a strange smell, like burnt oil,” she recalls.

The so-called oily sludge is a waste generated by oil storage, transport and processing. Depending on its composition, it may contain hydrocarbons and other potentially toxic chemicals.

Silva says that from that period onward many residents started linking the appearance of the material to a rise in serious illnesses among locals. Today, at 58, she lives with respiratory issues, chronic pain, glaucoma, depression and frequent shortness of breath. Her daughter has suffered persistent leg pain since adolescence, and her 8-year-old granddaughter has recurring respiratory problems.

She also recalls her mother’s health history. Before moving to the neighborhood, she used to lead an active life with no serious illnesses. Years later, she developed uterine cancer, lost vision in one eye due to another tumor and spent her final years with severe physical limitations.

There is no scientific proof that these cases are linked to the area’s environmental contamination. Residents argue, however, that the hypothesis has never been properly investigated by the government.

What the documents show

In the 2000s, investigations by environmental agencies began confirming what residents had already reported when they found sludge in backyards, streets and vacant lots. Over the years, technical analyses found oil-related contaminants in the soil and groundwater, while risk assessments indicated potential adverse effects for the population’s health.

Benzene was among the contaminants found. Brazil’s National Cancer Institute lists it as a highly toxic and carcinogenic substance with no safe exposure levels. It can cause blood abnormalities, affect the immune system and irritate ocular and respiratory mucous membranes. Prolonged exposure increases the risk of developing cancer and may lead to death in severe cases.

In 2011, Petrobras, the São Sebastião municipality and the São Paulo State Prosecution Service (MPSP) signed a Conduct Adjustment Commitment (TAC) to address the contamination’s effects. Seven years later, in 2018, an amendment included a Cross-Sectional Health Study to evaluate the potentially exposed population and investigate health outcomes linked to the area’s history.

The study would have become the main effort to answer a question that spans Itatinga’s entire history: Has environmental contamination impacted residents’ health?

Broken promise

The study, however, has never been conducted. The São Sebastião municipality says it took the necessary steps, but attempts at contracting resulted in “failed bidding processes,” with no “qualified institutions” submitting proposals. In addition to a lack of interested parties, the municipality justified abandoning the project by citing the “methodological complexity of the research” that required in-person household surveys, which became impossible during the COVID-19 pandemic.

In 2025, the study was replaced by a transfer of R$ 2.46 million ($479,122) to the city. The money was earmarked for the Municipal Land Regularization Fund under the second amendment to the Conduct Adjustment Commitment, and its actual disbursement remains subject to approval by the Prosecution Service’s Higher Council. The municipal administration has not disclosed whether any of the funds have been spent, and if so, how they were used.

Juliano Bueno is the director of Arayara, a leading Brazilian climate and environmental litigation organization. He says the study is important as it aims to answer a question that has remained open since the investigations began.

“You can’t say for sure that it is related. But you can’t say it isn’t either. The study was precisely a tool to answer that question,” said Bueno, who holds a Ph.D. in environmental risks and emergencies and another one in energy from the University of Lisbon.

For Bueno, replacing the study with financial compensation reveals a deeper problem: “The transfer turns the fundamental right to health and truth into a bargaining chip. Without the study, the problem cannot be measured, preventive actions cannot be planned, and adequate assistance cannot be offered to the population.”

In his view, the Itatinga case resembles what international literature calls a “sacrifice zone:” territories where socially vulnerable populations are exposed to persistent environmental risks while institutional responses focus on liability management rather than on human impacts.

“Soil is a medium; people are the end,” he said.

According to him, in order to be minimally fair for the community, any solution must rest on three pillars: Truth, reparation and guarantees of nonrepetition. Truth would rely on an independent epidemiological study. Reparation would involve providing permanent healthcare to the population and acknowledging the damage accumulated over decades. Guarantees of nonrepetition would require permanent environmental health monitoring mechanisms for communities exposed to contaminants such as benzene.

“Here, justice means restoring this community’s certainty that their lives are not disposable,” he concluded.

The impasse

Petrobras said there is no evidence linking the illnesses to contamination in the area. Even though it signed the Conduct Adjustment Commitment and carried out remediation works, the company told Mongabay that the land-filling and urbanization took place between the 1970s and 1980s, without its involvement. It says it is acting on the area’s rehabilitation out of “socio-environmental responsibility.”

Likewise, the São Sebastião municipality when contacted by Mongabay denied abnormal disease incidence and cited an Epidemiological Technical Report (2006-2026) to support its stance. The municipality stated the Oncology and Nephrology Support Center (CAON) recorded 25 patients in treatment in Itatinga over the past 10 years — an average of two to three cases per year, which would be comparable to other neighborhoods. The municipal administration, however, has not indicated whether this figure distinguishes between residents who actually live in the affected area or whether there is specific follow-up for the exposed population, noting that Itatinga has more than 5,000 residents.

CETESB, in turn, considers the remediated area safe for its current use, arguing that the site remains fenced off, without buildings and with only minor soil alterations. The state agency told Mongabay by email that no additional groundwater monitoring is needed, but complementary studies are still required on possible underground vapor intrusion in future occupation scenarios. CETESB says Petrobras should begin field work for this new analysis later this year.

For residents like Geraldo Ribeiro, a caretaker for his wife undergoing treatment for cancer, the technical justifications are not enough. The community’s core demand remains the same as it was two decades ago: “A study of the whole area is also a study of us. Because they have studied the land, but we are also here.”

Banner image: Itatinga resident Cosma da Silva shows her medical exam while describing her family’s battle with cancer. Image by Kico Santos.

This story was first published here in Portuguese on July 10, 2026.

Cite this article

Leandro Barbosa (2026). Health fears linger in a Brazilian neighborhood built over oil waste. Mongabay Conservation news. DOI: https://doi.org/10.66709/news-323738