As global cancer incidence trends shift, the world is witnessing an increase in cancer cases and a changing spectrum of cancer types. These trends are closely linked to environmental changes as a result of urbanization, with air and surface water pollution emerging as major public health concerns. There remains a dearth of effective strategies for evaluating environmental integrity, given the dynamic, cross-boundary nature of air and water pollution, along with the complex characteristics of pollutants such as their accumulation and heterogeneity. Different countries have distinct pollution-related challenges, and their measurement standards vary accordingly.

In this study, we propose an analytic framework to address these challenges by conducting a comprehensive analysis of the spatial distribution characteristics of air, water, and cancer in China. Built upon three national monitoring/registry databases, we developed a set of quantitative approaches to identify systemic interactions among pollutants in air and surface water and the incidence of 13 types of cancer. The goal of this research is to provide actionable insights and recommendations for harmonizing environmental changes with public health, fostering a pathway to sustainable development.

Innovative Design

By merging the ancient Chinese philosophy of "Unity of Nature and Man," proposed by Confucius and Mencius 2500 years ago, with the “Seed and Soil” theories proposed by Western scientists, our study philosophy goes beyond the previous pattern of piecewise studies in the realm of environmental and health research. The new resultant design, comprising the four core elements listed below, renders the evaluation of environmental pollution and public health more organic and provides novel solutions to practical problems.

1. Determining units of analysis and study areas

Owing to the varying scales of monitoring for the three components of interest (air, water, cancer), we first defined the analysis units to integrate them into a unified analytic framework. We defined the prefecture-level area as the basic unit. Any unit that simultaneously contained all three components (air monitoring site, water monitoring section, and cancer registry institute [CRI]) was included and denoted an analysis unit. All of these analysis units constituted the study area, covering a population of 377 million individuals. The design ensures the comprehensiveness and representativeness of the analysis.

2. Determining study components

We included six air pollutants recommended by the World Health Organization Global Air Quality Guidelines. We selected 13 types of surface water organic compounds based on their measurability, comprehensiveness, and pollution rates. We also chose 13 types of cancer with either rising incidence rates or lower survival rates to maximize the inclusion of pollutant types and cancer types present in the real world.

3. Characterizing pollution spatial distribution and establishing co-pollution levels

We divided pollution characteristics across 30 provinces and municipalities of mainland China into a "nine-grid" framework, illustrating the independent and combined effects of air and water pollution. By applying a method of merging similar items (based on the level of high pollution), we converted the pollution network into a one-dimensional scale (pollution degree) and quantified the impact of combined pollutants on the incidence of cancers. This enhanced our understanding of the comprehensive effects of complex polluted environments on health.

4. Developing a multi-approach analysis strategy

We used a mixed approach of classical statistics and machine learning techniques, on the basic assumption that random parameters (cancer incidence and annual average concentrations of pollutants) are random numbers, and we conducted a nationwide systematic analysis of the impact of multiple pollutants on various types of cancer. This integrated evaluation method not only reveals the complex relationships between pollutants and cancer incidence but also creates a comprehensive pollution index for stratified classification of pollution conditions in mainland China. Additionally, we carried out cancer attribution analysis to provide a thorough understanding of the impacts of co-pollution.

Key Findings

1. Joint effects of pollutants: As expected, we found a dose–response relationship between varying levels of co-pollution and cancer incidence, that is, pollutants in the air and surface water exhibited a joint effect on cancer onset.
2. Replication and expansion of existing evidence: Our study not only reaffirms existing evidence but also provides new insights, as outlined below.

• This study replicated the effects on lung cancer of particulate matter less than 2.5 micrometers in diameter, a proven carcinogen, with our results also demonstrating its association with leukemia.
• The association of nitrogen dioxide (NO2) with breast cancer has been confirmed, with some studies suggesting links to colorectal cancer and leukemia. This study not only replicated these results but also extended the impact of NO2 to six additional cancer types.
• Nitrosamines, produced by the reaction of nitrites with amines, are known carcinogens. Both direct carcinogens and procarcinogens can induce DNA changes. In this study, we revealed the association with three cancer types of COD_Mn, a comprehensive indicator of nitrites and organic pollutants in surface water.

3. Cancer clustering in poorer environments: Our findings confirm a clear trend in how cancer incidence varies with changes in the macroscopic environment, offering practical validation of the unity of nature and man concept and modern seed and soil theory.

Implications

1. Advancing health-related pollution standards: Our research is poised to drive the development of standards on pollutant regulation that are specifically designed to safeguard public health. By highlighting the potential health impact of pollutants, our findings will encourage policymakers to address these issues and implement measures to mitigate associated health risks.
2. Fostering cross-industry collaboration: Addressing cancer prevention requires a multi-sectoral approach. By integrating data originating from various industries, the results could be used to foster a consensus on health issues across sectors and stimulate collaborative efforts to tackle these challenges.
3. Promoting sustainable development: Economic progress should not come at the expense of environmental quality. On the basis of our study, we advocate for finding a balance during development, emphasizing that a healthy environment is crucial for long-term national stability and prosperity.
4. Encouraging international dialogue: The environmental challenges faced by China can be found in many other developing countries. Our research provides valuable insights for countries with similar problems, underscoring that environmental governance is a global issue requiring collective international action.

In conclusion, our study delivers innovative approaches and perspectives on how various pollutants affect cancer prevalence. We hope these insights will be instrumental in advancing human health and fostering development, setting the stage for future public health strategies and sustainable development projects.