Some questions remain buried long after the contaminated soil has been removed. Some aquifers carry more than water; they carry decades of uncertainty, silence, incomplete knowledge, and postponed answers. Beneath the volcanic landscape of Praia da Vitória lies one of the most consequential environmental stories in the modern history of the Azores, yet it is a story that has never been solely about contaminated land or polluted groundwater. At its deepest level, it has always been about people—about the invisible intersection between the natural environment and human lives, between scientific evidence and historical memory, between what has been carefully documented and what still remains unknown. It is a story that continues to challenge not only environmental policy but also our collective understanding of justice, responsibility, and the role of science in democratic societies.
The recent decision by the United States to maintain the designation “No Substantial Impact to Human Health and Safety” (NO-SIHHS) regarding the environmental contamination associated with Lajes Air Base deserves to be read with extraordinary care. Far too often, this classification has been interpreted as a declaration that no harm has ever occurred. It is, in fact, something much narrower—and far more revealing. The designation does not conclude that contamination never affected human health. Rather, it acknowledges that the scientific information currently available is insufficient to demonstrate that contamination produced a substantial impact on public health. That distinction may appear subtle to the casual reader, but it is, in both scientific and legal terms, profound. It separates what has been proven from what has never been adequately investigated. It reminds us that uncertainty is not the same as exoneration and that the absence of conclusive evidence cannot automatically be transformed into evidence that no harm ever existed.
Over more than three decades, environmental investigations have repeatedly confirmed the presence of petroleum hydrocarbons, aviation fuels, chlorinated solvents such as trichloroethylene (TCE) and tetrachloroethylene (PCE), benzene compounds, and numerous other contaminants in different sectors of Lajes Air Base and within the groundwater systems underlying Praia da Vitória. Successive technical studies have mapped contaminant plumes, monitored groundwater movement, identified polluted zones, and guided environmental remediation efforts that continue to this day. In that respect, the existence of environmental contamination is no longer the central question. The scientific literature has documented it extensively. What remains remarkably underdeveloped is the parallel investigation into human exposure. Who lived in those areas? Which water sources did they use? For how many years? Through what pathways might contaminants have entered the human body? What long-term health consequences, if any, resulted from those exposures? These questions have never received the same systematic scientific attention devoted to studying the contaminants themselves. The environmental story has been written in considerable detail; the human story remains largely unwritten.
This distinction carries enormous implications. Within scientific methodology, one of the most fundamental principles is that the absence of evidence cannot be mistaken for evidence of absence. A failure to demonstrate a causal relationship does not establish that no relationship exists; it simply indicates that sufficient evidence has not yet been produced. In legal settings, however, uncertainty often favors those who might otherwise bear responsibility. Without robust epidemiological data capable of linking exposure histories to measurable health outcomes, assigning liability becomes extraordinarily difficult. This is precisely where the Lajes case finds itself today. Environmental contamination has been documented. Human exposure has been assumed by many, suspected by others, but never reconstructed with the depth required to establish statistically meaningful conclusions. The result is an enduring scientific gap that continues to shape every discussion surrounding the site.
The significance of that gap becomes even clearer when the Azorean experience is compared with major contamination cases elsewhere. Camp Lejeune, in North Carolina, remains one of the most extensively studied examples of military groundwater contamination in the United States. There, investigators also identified TCE, PCE, benzene, and other volatile organic compounds contaminating drinking water systems used for decades by military personnel, civilian workers, and their families. Yet the recognition of associated health effects did not emerge immediately. It followed years of painstaking scientific work. Researchers reconstructed historical water distribution systems, modeled groundwater behavior over time, estimated historical contaminant concentrations, identified tens of thousands of individuals potentially exposed, and compared disease patterns across large populations. Only after this enormous body of work did statistically significant associations emerge between prolonged exposure and specific illnesses. Those findings eventually became the scientific foundation for federal recognition of presumptive diseases and compensation programs for affected veterans and families. The essential lesson of Camp Lejeune is not merely that contamination existed; it is that science was given the opportunity to investigate human exposure with extraordinary depth before conclusions were reached.
A similar lesson emerges from Kelly Air Force Base in Texas. Although that case followed a different legal trajectory, the scientific response extended well beyond environmental monitoring. Investigations integrated hydrogeology, toxicology, environmental chemistry, exposure assessment, vapor intrusion studies, long-term environmental surveillance, and risk evaluation for neighboring communities. The objective was not simply to determine where contaminants had migrated beneath the surface. It was to understand whether those contaminants had entered people’s daily lives through drinking water, soil, indoor air, or occupational exposure. The question evolved from “Where is the contamination?” to “Who may have been exposed?” That second question continues to define the greatest scientific absence in the history of Lajes Air Base.
Current monitoring programs for public drinking water in Praia da Vitória indicate that water supplied today generally complies with legal quality standards. That fact should not be dismissed; it represents an important achievement in protecting current public health. Yet it answers only a contemporary question. It tells us about water quality at the moment samples are collected. It tells us very little about conditions twenty, thirty, or forty years ago. Groundwater systems are dynamic rather than static. Contaminant concentrations shift over time as aquifers recharge, rainfall patterns fluctuate, pumping regimes change, and contaminant plumes migrate beneath the surface. Periodic sampling campaigns provide valuable snapshots, but they cannot reconstruct decades of historical exposure on their own. Environmental epidemiologists have long emphasized that chronic exposure differs fundamentally from acute intoxication. Bioaccumulation occurs quietly, often through the repeated absorption of extremely small quantities of contaminants over many years. Even when individual exposures remain below regulatory thresholds, persistent accumulation may eventually affect bones, kidneys, liver, fatty tissues, or other organs. Understanding such processes requires historical reconstruction rather than contemporary monitoring alone.
Recent research conducted at the University of Coimbra has added another important dimension to this discussion by identifying elevated concentrations of heavy metals in human skeletal remains recovered from Praia da Vitória. The study demonstrates that these individuals experienced exposure to substances such as lead and cadmium during their lifetimes. At the same time, the researchers have appropriately emphasized the limits of their findings. Their work does not identify the precise origin of those contaminants, does not establish that exposure resulted specifically from activities at Lajes Air Base, and does not demonstrate direct causal relationships between those findings and specific diseases. Nevertheless, the study reinforces a central scientific reality: human exposure occurred. What remains uncertain are the origin, duration, intensity, pathways, and clinical consequences of that exposure. Resolving those questions would require precisely the multidisciplinary research framework that has yet to be implemented.
Many specialists believe that such an investigation remains scientifically possible even today. Although time inevitably erases part of the historical record, modern environmental epidemiology routinely reconstructs exposure scenarios decades after the original events occurred. Historical water distribution systems can be reconstructed. Groundwater models can be developed retrospectively. Former residents and workers can be identified. Epidemiological cohorts can be established. Biomonitoring studies can be designed. Comparisons with populations lacking known environmental exposure can be performed. None of these approaches can eliminate uncertainty entirely, but together they can substantially reduce it. What is absent in the Azorean case is not scientific capability. It is the sustained commitment required to pursue such research with the same determination witnessed in other internationally recognized contamination cases.
Unfortunately, discussions surrounding Lajes have too often become polarized between political accusation and institutional defense. Neither serves science particularly well. Scientific inquiry exists neither to vindicate institutions nor to confirm suspicions in the absence of evidence. Its purpose is to investigate rigorously, to challenge assumptions, to reduce uncertainty, and to approach the truth as closely as available evidence permits. The greatest difference between Lajes and sites such as Camp Lejeune or Kelly Air Force Base may therefore lie not in the nature of the contaminants—which are strikingly similar—but in the depth of investigation directed toward the populations potentially exposed. Camp Lejeune became one of the world’s best documented environmental health investigations. Kelly integrated environmental contamination with comprehensive human exposure analysis. Lajes has remained, for the most part, an environmental remediation story without a correspondingly ambitious epidemiological chapter. That difference helps explain why the NO-SIHHS classification remains in place—not because science has demonstrated that no public health effects ever occurred, but because the scientific evidence required to establish such conclusions has never been assembled.
Ultimately, the central question surrounding Lajes has never changed. It is not simply whether contaminants entered the soil or the groundwater; decades of investigation have already answered that. The deeper question is whether those contaminants entered people’s lives in ways that continue to matter today. That question cannot be resolved through political rhetoric, institutional reassurance, or public speculation. It demands rigorous, multidisciplinary science bringing together hydrogeology, toxicology, environmental medicine, biomonitoring, and epidemiology. Until such work is undertaken, one of the most important environmental chapters in modern Azorean history will remain fundamentally incomplete—not because too little is known about contaminated land, but because too little is known about those who may have lived alongside it. Contaminated soil can eventually be remediated. Aquifers can slowly recover. But uncertainty, once allowed to settle across generations, becomes far more difficult to remove. The greatest responsibility now is not merely to continue cleaning the land. It is to pursue, with intellectual honesty and scientific courage, the answers that the land itself can no longer provide. Only then will the story of Lajes cease to be a history of contamination and become, finally, a history of understanding.
Based on a story published in Diário Insular-José Lourenço, director. Photos from Diário Insular and JEdgardo Vieira.
