Mapping and visualizing the global research landscapes on drinking water and cancer

Abstract

A growing body of epidemiologic research has examined the potential associations between contaminants in drinking water and various cancers, with a special emphasis on sources of particular concern, including arsenic, asbestos, radon, agricultural chemicals, and byproducts of hazardous waste sites. Given the potential public health implications, a bibliometric analysis of the literature in this field is warranted. This analysis aims to systematically map the progression of research on the relationship between drinking water contaminants and cancer. By identifying emerging trends and knowledge gaps, this analysis can inform future research directions and prioritize areas with the greatest potential for public health impact. In this study, we employed a bibliometric approach to analyze research on drinking water and cancer. We searched for articles in all languages published between 1939 and 2023 using the Scopus database. To ensure the precision of our search, we validated a search strategy using relevant keywords related to drinking water and cancer. The data analysis included bibliometric indicators such as the analysis of citation patterns, publication trends, and the identification of the most productive countries and institutions in this field. Finally, we used VOSviewer software (version 1.6.20) to visualize the data through network and co-occurrence analysis. This visualization helped us identify key research clusters and emerging topics within the field. A comprehensive search of the Scopus database from 1939 to 2023 yielded 11,703 articles related to drinking water and cancer. By focusing on journal articles and excluding errata and retracted documents, the data set was refined to 10,751 publications. The majority (91.06%) of these were original research articles (n = 9790), while reviews accounted for 6.49% (n = 698). The United States was the country that contributed the most articles in this field, contributing 3,268 articles (30.4%), followed by China (n = 1496; 13.9%), Japan (n = 1358; 12.6%), and India (n = 758; 7.1%). Recent research (post-2015) focuses on assessing carcinogenic pollutant risks, mainly in groundwater. In contrast, earlier studies often used animal and human models to explore the carcinogenic effects of various chemicals found in drinking water. This study offers insight into the current research on the link between contaminants in drinking water and cancer. Most of this research focuses on high-income countries, highlighting the need for more studies in low- and middle-income regions. To advance our understanding and develop effective strategies, further research is essential. This includes improving methods for detecting and measuring emerging contaminants, as well as evaluating the impact of water treatment and sanitation practices.

Article Highlights

Cancer and drinking water global knowledge is analyzed using performance analysis and visualization mapping.

More research is required to effectively detect emerging contaminants and investigate water treatment and sanitation impacts.

Most cancer-drinking water research originates in developed countries, stressing the significance of collaboration and investments.

Introduction

Different chemicals are introduced into our water supplies by human activities. These substances may enter the system through infiltration during transit, treatment byproducts, or contamination at the source [1]. Depending on where they originate, these possible carcinogens (agents that cause cancer) in our drinking water can take many different forms and at different concentrations [1]. Hazardous waste, radon, asbestos, arsenic, and agricultural chemicals can contaminate source water. Arsenic is the most carcinogenic; it has been associated with cancers of the liver, lungs, bladder, and kidneys [2]. One of the most important steps in preventing infectious diseases is chlorine disinfection, which can also produce disinfection by products (DBPs) that may be carcinogenic [3]. There is evidence that prolonged exposure to water contaminants, even at levels found in drinking water, can increase the risk of disease [4]. Access to clean water is perhaps the most important public health intervention [5].

DBPs in drinking water have been associated with an increased risk of bladder, colon, and rectal cancers, according to epidemiological studies (evidence based on disease patterns) [6–8]. An increased risk of bladder and rectal cancers has also been associated with long-term exposure to chlorinated surface water, which is a source of DBPs [9]. Furthermore, proximal colon cancer in men has been associated with an elevated risk of colorectal cancer in association with high levels of trihalomethanes (a kind of DBPs) in drinking water [10]. Similarly, exposure to trihalomethanes and nitrate has been associated with a greater risk of colorectal cancer, possibly due to inflammatory processes [11].

Bibliometrics is a scientific method that employs mathematical and statistical techniques to quantitatively analyze a knowledge system. It is used to analyze, compare, and quantify the literature to better understand the evolution and patterns of scientific research[12–14]. Although numerous bibliometric studies have examined research productivity in the environmental field [15–19], including studies on drinking water [20–24] and cancer [25–30], there has yet to be an evaluation of research output on the relationship between drinking water and cancer. This study conducts a bibliometric analysis of the literature in this field to better understand the progression of the literature on the relationship between drinking water and cancer. The purpose of this project is to identify specific areas of interest that could be useful for future research. This study evaluated data that will help fill research gaps in this area. The current bibliometric analysis is extremely valuable for researchers studying the link between drinking water and cancer. It is a concise reference tool for interdisciplinary researchers, providing an overview of recent scientific evaluations on this topic.

Methods

Study design

Performance analysis and bibliometric methods were applied to conduct a descriptive cross-sectional assessment of published works associated with cancer and drinking water. Over a decade, bibliometric analyses have emerged as the focus of several scholarly works, covering a broad spectrum of scientific topics [31–35]. Unlike systematic reviews, which address specific research issues based on a limited selection of research works [36], and scoping reviews, which aim to outline the scope and features of research evidence [37], bibliometric methods deliver an effective resource to capture an overview of both national and international contributions to the literature in a specific field. Bibliometric methods, in addition, offer significant data to identify research gaps and guide future investigations toward potential domains of attention [38].

Database used

A comprehensive bibliometric analysis implies the application of multiple databases of literature for extensive document analysis. However, when confronted with a large body of literature on the topic in question, this approach could be impractical. In view of the challenging task of applying bibliometric metrics and mapping literature within multiple databases (e.g., overlapping or repetitive publications), bibliometric studies typically employ a single database [39] to avoid compromising the reliability of the research results [40]. The present analysis covers a significant amount of literature (10,751 documents), justifying the application of a single database. A survey of the literature revealed that the Scopus database is one of the most comprehensive literature databases in the context of data size and the affordability of analytical and sorting capabilities [41, 42]. It offers extensive coverage, including all PubMed content, as well as twofold the number of indexed sources and journals as of Web of Science. It offers comprehensive author and institution profiles compiled using advanced profiling algorithms, ensuring excellent precision and reliability [43]. Consequently, Scopus was suggested by the investigators of the present analysis for fulfilling the research objectives. Scopus’s robust search functions are extremely advantageous, facilitating the design of comprehensive and complex queries for searching [44]. This includes using Boolean operators (e.g., AND, OR, and NOT) to combine search terms in appropriate search queries, field specific search (e.g., title, abstract, author name, source title, or keywords), wildcard and truncation for flexible keyword variations, proximity search to finds terms that are within a certain distance from each other, phrase search, and citation search [45].

Search strategy

A comprehensive search of the Scopus database identified relevant research on cancer and drinking water. The search process was not restricted to a particular starting time but was restricted to covering all data and research works available until the end of 2023. This time frame allowed the identification of major shifts, progress, or declines in research outputs and impact over time, thus facilitating an overview of emerging trends and advancements. This ensures that the results of the analysis are timely and pertinent. To eliminate possible biases triggered by continuous database updates, all relevant search operations and data retrieved were compiled in a single session, April 8, 2024. This analysis applied an explicit and rigorous search strategy that incorporated advanced search tools, addressing an extensive array of concepts and terms related to drinking water and cancer. The data of this analysis were acquired by applying the following consecutive steps:

Step 1: To successfully identify pertinent search terms, a literature review was performed on the association between drinking water and cancer, focusing specifically on systematic reviews and meta-analyses [46–48].

Step 2: Cancer-related terms were retrieved via PubMed’s Medical Subject Headings (MeSH) along with previous research [29, 49]. Drinking water terms were drawn from an array of bibliometric analyses, each exploring a specific topic and context within the broader issue of drinking water [21, 24, 50–52].

Step 3: The search query was limited to terms related to cancer and drinking water in the titles and abstracts of documents. It was only applied to journals as a source, and it discarded errata and retracted documents from the journal’s output. The concluding search query was as follows: (( TITLE-ABS(Drinking Water OR Potable Water OR Bottled Water) AND TITLE-ABS ( cancer OR carcinoma OR malignancies OR malignant OR malignancy OR neoplasia OR neoplasm OR tumour OR tumor) OR TITLE-ABS ( carcinogen* OR tumorigenesis OR tumorigeneses OR oncogenesis OR oncogeneses) OR TITLE-ABS ( oncology)) AND PUBYEAR < 2024 AND PUBYEAR > 1938 AND PUBYEAR < 2024 AND (LIMIT-TO (SRCTYPE,"j")) AND (EXCLUDE (DOCTYPE,"er") OR EXCLUDE (DOCTYPE,"tb"))).

Step 4: The search query was scrutinized by applying two techniques. First, two external colleagues in the field of bibliometric science examined the titles and abstracts of the 100 most cited documents, delivered as an Endnote folder (Endnote ™; version: 20, Clarivate Analytics, New York, NY, USA). Second, the lead investigator verified the titles and abstracts of publications in even numbers (110, 120, 130, 140, etc.) to verify content credibility.

Bibliometric and performance analysis

In the present analysis, the basic bibliometric metrics that were investigated were classified into four major groups, either quantitative or qualitative indicators:

1. Research Evolution: This category explored publication years, evolution patterns with time, and citation counts.

2. Origin of the published works: This category analyzed the productive countries and origins that contributed to research related to cancer and drinking water.

3. Research productivity: This category recognized the major institutions and funding agencies active in the field under investigation.

4. Impact of research: This category investigated the significance of highly cited research works, the Hirsch index (h index), and renowned journals, including their impact factors.

Visualization analysis

VOSviewer software, developed by the Center for Science and Technology Studies at Leiden University in the Netherlands, is applied to develop network maps and knowledge structures that reveal global collaboration, intellectual links between sources, and research-driving themes [53, 54]. VOSviewer provides a two-dimensional bibliometric map that reveals collaboration among countries, institutions, authors, etc. [54]. The distance between two countries on the map, for example, represents the extent of association, with shorter distances implying close scientific collaboration. VOSviewer categorizes countries into distinct clusters based on frequent collaboration within each group. Co-citation analysis, which explores shared citations among sources, is utilized to determine associations between different publications and acquire a better understanding of intellectual associations between major journals. The evidence of a similarity between B and C journals, for example, could come from an article in journal A citing works from both journals B and C. The greater the association, the more documents in other journals that cite both B and C journals [55]. Co-citation links between two journals display their relationship based on their proximity on the visualization map [54]. VOSviewer aggregates sources into distinct clusters, each exhibiting a closely related field. Such an analysis enables researchers to recognize fundamental journals in the field under investigation [56]. Using keyword co-occurrence analysis, VOSviewer depicted each term by a frame. The size of the frame is correlated with the total number of published works corresponding to that term [57]. To highlight topics of interest, the relevant terms of the titles and abstracts were selected. This analysis showed the extent to which two terms occurred simultaneously in different published works, proving the level of similarity [58]. The co-occurrence analysis utilized the value of a relevance score. This score omits general terms and only considers terms that have higher relevance scores, which consistently underscores significant topics [54]. Figure 1 summarizes the methodological strategy, detailing the inclusion criteria and analysis techniques.

Fig. 1 [Images not available. See PDF.]

The roadmap outlines the entire analysis procedure of knowledge on drinking water-cancer, including data collection, bibliometric analysis, visualization mapping, and major outcomes

Results

Volume of published works on cancer and drinking water

The earliest document indexed in the Scopus database on the topic under investigation dates back to 1939. From 1939 to the end of 2023, 11,703 documents of different types were identified in the Scopus database on cancer and drinking water-related research. When considering the content published in journals as the primary source only, omitting errors and retracted documents, 10,751 documents were identified. These were divided into articles (9790 documents; 91.06%), reviews (698 documents; 6.49%), and conference papers (184 documents; 1.71%). Other less-represented types (79 documents; 0.73%) involved letters, notes, short surveys, editorials, and data papers.

Evolution and productivity trends

Figure 2 shows the evolution of published works on cancer and drinking water over eight decades. Productivity rates began modestly, specifically in the first three decades. However, the number of published works has grown substantially over the last five years. The graph reveals an exponential increase in research related to cancer and drinking water, with a determination coefficient R² = 0.891. There was a strong positive correlation between the annual publication count and the corresponding year of publication (P < 0.001).

Fig. 2 [Images not available. See PDF.]

The evolution of cancer and drinking water-related publications

Performance of global regions and countries

Figure 3 reveals a detailed visualization of the global output of cancer and drinking water research, with participation from 143 countries of various capacities. The Asiatic region is the most prolific region at the regional level, yielding 4713 documents (43.8% of the total). This region is followed by North America (3612 documents; 33.6%), Western Europe (2165 documents; 20.1%), the Middle East (810 documents; 7.5%), Eastern Europe (580 documents; 5.4%), Africa (530 documents; 4.9%), Latin America (465 documents; 4.3%), and the Pacific region (221 documents; 2.1%). Africa has the most contributing countries at 30, with Nigeria leading (152 documents). The Asiatic region is second with 27 countries, led by China (1496 documents). Eastern Europe features 22, with the Russian Federation in the core (181 documents), Latin America (20) with Brazil at the forefront (188 documents), Western Europe (20) with Germany leading (399 documents), the Middle East (16) with Iran in the core (306 documents), and the Pacific region (6) with Australia leading in this regard (185 documents). Finally, North America features 2 contributing countries, with the United States as the most influential (3268 documents).

Fig. 3 [Images not available. See PDF.]

Nation–level production on cancer-drinking water research; a worldwide perspective of research productivity at the country (or region) level. The size of the black circles represents the output of each country (or region) (i.e., the larger the circle is, the greater the performance of the country or a region with respect to the number of publications). The colors further indicate the productivity of each country, using a range of shades to differentiate countries based on their productivity levels. The global map was created using Statplanet Interactive Mapping and Visualization Software, www.statsilk.com, free license

Table 1 presents the top ten countries sorted by their research productivity at the country level. The United States dominates the list, accounting for approximately one-third of all publications on cancer and drinking water. China and Japan follow at a distance. The top ten most productive countries collectively contributed 7935 documents, which is 73.8% of the total. This figure underscores the crucial role these countries undertake in producing the bulk of global knowledge in this regard. The findings demonstrate incompatible collaboration trends among the most productive countries, as well as between these countries and those not in the top ten list. Collaboration rates surpass 40% for the United Kingdom, Canada, Italy, and Germany, while for other countries, the rates range from 18.1% to 29.4%. There is an overlap in research output across countries, developing when researchers from different countries work jointly on research projects or when specific research is assigned to several countries.

Table 1. The top 10 most productive countries on research related to cancer and drinking water

Rank	Country/Territory	# of documents	%	# collaborated countries	# of documents from collaboration (%)	Most collaborated country	# of documents with most collaborated country (%)
1st	United States	3268	30.4	92	925 (28.3)	China	158 (4.8)
2nd	China	1496	13.9	58	358 (23.9)	United States	158 (10.6)
3rd	Japan	1358	12.6	56	257 (18.9)	United States	111(8.2)
4th	India	758	7.1	60	184 (24.3)	United States	54 (7.1)
5th	Germany	399	3.7	63	161(40.3)	United States	54 (13.5)
6th	United Kingdom	380	3.5	63	209 (55.0)	United States	73 (19.2)
7th	Canada	344	3.2	46	170 (49.4)	United States	89 (25.9)
8th	Iran	306	2.8	45	90 (29.4)	United States	21 (6.9)
9th	Italy	266	2.5	62	128 (48.1)	United States	40 (15.0)
10th	Taiwan	237	2.2	22	43 (18.1)	United States	29 (12.2)

Figure 4 shows the scale of global research collaboration between countries, highlighting countries that have contributed more than 100 documents on cancer and drinking water research. The map shows 25 countries organized into three major clusters. Cluster 1, in red, is made up primarily of Asian countries; cluster 2, in green, comprises primarily Western European countries; and cluster 3, in blue, consists mainly of Latin American countries. The United States stands at the center of the map, with the highest number of collaboration links (24 links out of 244 total links) and the greatest strength of significant links (940 out of 2218).

Fig. 4 [Images not available. See PDF.]

Visualization map of international research collaboration with a minimum research output of 100 documents/country. Of the 143 countries, 25 met this threshold. Full counting is employed, where each co-authorship link is assigned equal weight. For each of the 25 countries, the total strength of the co-authorship links with other countries was calculated. The countries with the highest total link strength were selected. The map categorized the countries that most frequently collaborated into 3 clusters with distinctive colors: Cluster 1 with red (11 countries; the United States acquired the strongest link strength: 940 out of 2218, and the greatest number of links: 24 out of 244); Cluster 2 with green (9 countries; the United Kingdom acquired the strongest link strength: 271 out of 2218 and the greatest number of links: 23 each out of 244); and Cluster 3 with blue (5 countries; India acquired the strongest link strength: 220 out of 2218 and recorded the greatest number of links: 24 out of 244). Co-authorship links between the United States and China (link strength: 158), Japan (link strength: 108), Canada (link strength: 89), the United Kingdom (link strength: 71), and Germany (link strength: 53) were the strongest links at the global level. The map was created using VOSviewer software version 1.6.20

Top institutions/organizations

Table 2 lists the 10 most significant institutions out of 24,056 that are actively researching cancer and drinking water. These institutions collectively produced 1385 documents, accounting for 12.6% of all published works in the field. The United States Environmental Protection Agency (EPA) was the most prolific organization, with 225 documents (2.1%). It is followed by the National Institute of Health Sciences, Japan, which has 180 documents (1.7%). Of the ten most active institutions, six were from the United States, three were from Japan, and two were from China.

Table 2. The top 10 most productive institutions/organizations on research related to cancer and drinking water

Rank	Affiliation	Country	# of documents	%
1st	United States Environmental Protection Agency	United States	225	2.1
2nd	National Institute of Health Sciences	Japan	180	1.7
3rd	Chinese Academy of Sciences	China	167	1.6
4th	Ministry of Education of the People's Republic of China	China	158	1.5
4th	National Cancer Institute NCI	United States	158	1.5
6th	Nagoya City University Medical School	Japan	138	1.3
7th	University of Nebraska Medical Center	United States	137	1.3
8th	National Cancer Institute at Frederick	United States	121	1.1
9th	Osaka Metropolitan University Graduate School of Medicine	Japan	98	0.9
10th	National Institutes of Health NIH	United States	94	0.9
10th	US EPA National Health and Environmental Effects Research Laboratory	United States	94	0.9

Major funding organizations/agencies

Table 3 lists the 10 most significant funding agencies that have contributed to this field. The National Cancer Institute, the United States (n = 626; 5.8%), the National Natural Science Foundation of China (n = 493; 4.6%), the National Institutes of Health, the United States (n = 416; 3.9%), and the National Institute of Environmental Health Sciences, the United States (n = 403; 3.7%), are the leading funding agencies. Collectively, the agencies listed as top funding supported 2058 research works (19.1% of the total publications). It should be highlighted that the United States has assumed an essential role in this field, with five of the active funding agencies based in this country. It is followed by Japan, which has three funding agencies.

Table 3. The top 10 funding agencies that support research related to cancer and drinking water

Rank	Funding sponsor	Country	# of documents	%
1st	National Cancer Institute	United States	626	5.8
2nd	National Natural Science Foundation of China	China	493	4.6
3rd	National Institutes of Health	United States	416	3.9
4th	National Institute of Environmental Health Sciences	United States	403	3.7
5th	Ministry of Education, Culture, Sports, Science and Technology	Japan	132	1.2
6th	Japan Society for the Promotion of Science	Japan	126	1.2
7th	U.S. Environmental Protection Agency	United States	119	1.1
8th	Ministry of Health, Labour and Welfare	Japan	118	1.1
9th	U.S. Public Health Service	United States	79	0.7
10th	Department of Science and Technology, Ministry of Science and Technology, India	India	74	0.7

Major journals

Table 4 shows the top ten journals out of 2481 journals that contributed to cancer and drinking water, sorted by publication. These journals delivered a total of 1676 documents, which is 15.6% of all contributions in the field. Carcinogenesis dominated with 296 documents, accounting for 2.8% of the total. The Cancer Research journal features 254 documents (2.4%), preceding Cancer Letters featuring 192 documents (1.8%), and the Science of the Total Environment journal with 157 documents (1.5%). These respected journals span three pertinent fields: carcinogenicity, toxicology, and environmental sciences. The impact factor and CiteScore metrics highlight the significant influence of these journals in the field under investigation.

Table 4. The journals with the most publications on cancer and drinking water

Rank	Source	# of documents	%	IFa	CiteScoreb
1st	Carcinogenesis	296	2.8	4.7	8.4
2nd	Cancer Research	254	2.4	11.2	16.9
3rd	Cancer Letters	192	1.8	9.7	16.7
4th	Science of the Total Environment	157	1.5	9.8	16.8
5th	Journal of the National Cancer Institute	149	1.4	10.3	18.3
6th	Environmental Health Perspectives	140	1.3	10.4	15.2
7th	Environmental Science and Pollution Research	133	1.2	5.8	7.9
8th	Toxicology and Applied Pharmacology	124	1.2	3.8	7.2
9th	Chemosphere	118	1.1	8.8	13.3
10th	Food and Chemical Toxicology	113	1.1	4.3	11.2

^a Impact Factor (IF): This factor is calculated by dividing the number of current-year citations by the number of source items published in a journal during the previous 2 years (these include articles, reviews, and proceedings papers) (2022 Journal Citation Reports®, Clarivate 2023)

^b CiteScore: CiteScore 2022 counts the citations received from 2019 to 2022 for articles, reviews, conference papers, book chapters, and data papers published from 2019 to 2022 and divides this by the number of publications published from 2019 to 2022 (CiteScore 2022, Scopus database 2023)

Analysis of citation figures

According to the citation analysis, the retrieved documents acquired an average of 37.7 citations per document, with an h-index of 223 and a total of 405,258 citations. Of these documents, 859 did not receive citations, while 906 acquired more than 100 citations/document. The numbers of references for these studies fluctuated between 0 and 4728. Table 5 lists the 10 most cited documents; eight are reviews, and two are articles [46, 47, 59–66]. The number of citations for the documents included in the list varied from 984 to 4728 at the time the data were compiled and analyzed.

Table 5. The top 10 documents most cited in cancer and drinking water-related research

Rank	Authors	Year	Title	Source title	Cited by	Document type
1st	Järup L	2003	“Hazards of heavy metal contamination”	British Medical Bulletin	4728	Review
2nd	Richardson S.D. et al	2007	“Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research”	Mutation Research—Reviews in Mutation Research	2631	Review
3rd	Smith A.H. et al	2000	“Contamination of drinking-water by arsenic in Bangladesh: A public health emergency”	Bulletin of the World Health Organization	1682	Article
4th	Camargo J.A. and Alonso Á	2006	“Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems: A global assessment”	Environment International	1557	Review
5th	Weber L.W.D. et al	2003	“Hepatotoxicity and mechanism of action of haloalkanes: Carbon tetrachloride as a toxicological model”	Critical Reviews in Toxicology	1439	Review
6th	Kim K.-H. et al	2017	“Exposure to pesticides and the associated human health effects”	Science of the Total Environment	1199	Review
7th	Sunderland E.M. et al	2019	“A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects”	Journal of Exposure Science and Environmental Epidemiology	1141	Review
8th	Fendorf S. et al	2010	“Spatial and temporal variations of groundwater arsenic in South and Southeast Asia”	Science	995	Review
9th	Naujokas M.F. et al	2013	“The broad scope of health effects from chronic arsenic exposure: Update on a worldwide public health problem”	Environmental Health Perspectives	993	Review
10th	Hughes M.F. et al	2011	“Arsenic exposure and toxicology: A historical perspective”	Toxicological Sciences	984	Article

Analysis of co-citation figures

Figure 5 illustrates the 11 most influential journals that have substantial co-citation links, achieving a minimum citation threshold of 2000. These journals contribute significantly to sharing knowledge and providing solid insights into cancer and drinking water. The map organizes these journals into three distinct clusters, each highlighted with a distinctive color, according to shared attributes (e.g., similar research themes, topics, or methodologies), indicating that journals within each cluster are related in the academic landscape. The red cluster is composed of five journals, with Carcinogenesis journal at the center of this cluster. The green cluster, consisting of 4 journals, has the Environmental Science and Technology journal at its core. The blue cluster features only 2 journals, the core is Mutation Research journal. The map indicates the close association between Water Research and Environmental Science and Technology, which was recognized as the most substantial link on the map (the thickest line). Moreover, there was a significant association between Carcinogenesis and Cancer Research. The map reveals a dominant position of journals with emphasis on water, environmental, carcinogenicity, and toxicology research.

Fig. 5 [Images not available. See PDF.]

Network visualization map. The minimum number of citations of a source was set as 2000. Full counting is employed, where each co-citation link is assigned equal weight. Of the 76,012 sources, 11 met the threshold. For each of the 11 sources, the total strength of the co-citation links with other sources was calculated. The sources with the highest total link strength were selected. The map categorized the most co-cited sources into 3 clusters with distinctive colors: Cluster 1 with red (5 sources); Cluster 2 with green (4 sources); and Cluster 3 with blue (2 sources). The map was created using VOSviewer software version 1.6.20

Keyword co-occurrence analysis

VOSviewer was applied to perform a co-occurrence analysis of the titles and abstracts of documents related to cancer and drinking water. The main research themes are displayed in Fig. 6. Diverse research themes have been displayed employing network visualization, which maps the co-occurrence of terms more than 200 times. Of the 162,034 terms, 166 satisfied the threshold, based on a relevance score of 60%, which omits the general terms, and were assigned to two major groups (Fig. 6). Each of the clusters is distinguished by a distinctive color: red for cluster 1 and green for cluster 2, which indicate terms relevant to specific research topics. Cluster 1 focused mainly on drinking water quality and health risk assessment, which involved evaluating different contaminants and their associated health hazards. This involves accomplishing risk assessments, monitoring initiatives, and imposing regulations that preserve safety and quality. It investigates the prevalence, occurrence, and impacts of chemical contaminants in drinking water sources, focusing primarily on heavy metals, DBPs, and other hazardous substances. Cluster 2 is devoted to experimental research that involves animal and human models to explore the carcinogenic repercussions of many different chemicals and substances that exist in drinking water. It addresses the molecular and cellular mechanisms that explain carcinogenesis, targeting modifications in gene expression, proliferation of cells, and responses to inflammation. The terms in each cluster revealed substantial associations that demonstrated the consistency of the research within these themes.

Fig. 6 [Images not available. See PDF.]

Network visualization map of term co-occurrence within title-abstract. Two hundred occurrences of a term were set as the minimum number (Binary counting: involves assessing the presence or absence of a term in the titles and abstracts of documents, with the frequency of occurrences within a document being disregarded). A total of 166 terms out of the 162,034 terms met the set threshold considering a relevance score of 60%. Terms are categorized into 2 major clusters: Cluster 1, red (85 items); and Cluster 2, green (81 items). The map was created using VOSviewer software version 1.6.20

Research trends

The terms prevalent in research on cancer and drinking water over time were additionally recognized in the titles and abstracts through keyword co-occurrence analysis (Fig. 7). In particular, studies exploring risk assessments, focusing on both carcinogenic and noncarcinogenic contaminants, using hazard quotients and other indices to quantify and prioritize risk levels, and examining groundwater samples for hazardous substances impacting public health have emerged in recent years since earlier research focused on experimental models.

Fig. 7 [Images not available. See PDF.]

Overlay visualization map of term co-occurrence within the title-abstract. Two hundred occurrences of a term were set as the minimum number (Binary counting: involves assessing the presence or absence of a term in the titles and abstracts of documents, with the frequency of occurrences within a document being disregarded). A total of 166 terms out of the 162,034 terms met the set threshold considering a relevance score of 60%. The blue nodes represent earlier occurrences, and the yellow nodes represent later occurrences. The map was created using VOSviewer software version 1.6.20

Discussion

In this paper, a bibliometric analysis of the scientific literature on drinking water and its possible association with cancer is presented. Our research focused on studies that examined the relationship between the development of cancer and different toxic substances and compounds, such as heavy metals, that are present in drinking water. Although previous bibliometric reviews have examined specific water contaminants such as lead, arsenic, or Cryptosporidium [21, 22, 52, 67, 68], no research has examined the total cancer risk associated with the exposure of drinking water to dangerous elements. Furthermore, the specific link between water quality and cancer has not been examined in bibliometric analyses of water that have been performed thus far, instead of focusing on general water quality or water treatment technologies [20–22, 24, 52, 69]. Here, we seek to close this gap by undertaking an extensive analysis of drinking water-related cancer research covering a wide range of potential cancer-causing agents.

The development of drinking water quality and the productivity of cancer research over time have been influenced by several factors, including population growth, industrialization, water scarcity, policy changes, and technological advances. Proactive strategic planning, investments in infrastructure and research, and the implementation of regulatory measures have all been necessary to address these issues. Furthermore, advances in science and technology have significantly impacted the productivity of cancer research and the trajectory of drinking water quality. Cancer continues to be the leading cause of global mortality and morbidity, with its incidence estimated to increase by 50% over the next two decades. Finding associated environmental risk factors is crucial, as evidenced by daily increases in most cancer types [6, 70]. DBPs in drinking water have been linked by epidemiological evidence to a number of cancers, including those of the gastrointestinal tract, kidney, bladder, breast, liver, and thyroid [3, 6, 71]. Consequently, several factors have aided in the growth of the research trajectory: (1) Proactive strategic planning is necessary in light of global water scarcity caused by population growth, industrial pollution, and climate change [72]. (2) Investments in infrastructure, research, and human resources are essential for creative water quality management [72]. (3) Concerns about wastewater production and the availability of clean drinking water have increased due to increasing industrialization and population density [73]. (4) The world's need for water has increased dramatically due to the rapid growth of the industrial sector and population [74]. (5) The growing shortage of fresh water, exacerbated by pollution and depletion, has become a worldwide concern that affects more than 1.2 billion people [75, 76].

The number of related research publications has increased due to the growing global concern about water quality and its possible link to cancer. There are countries with distinct research priorities, such as the United States, China, Japan, and India. These include examining the sources of drinking water and learning how different pollutants are geographically distributed within water bodies and how these elements affect different types of cancer. Converting these research results into useful public health interventions and policies is the ultimate objective [77]. The development of effective preventive measures, improved international collaboration, and development grounded in scientific evidence have been identified as research priorities for future investigations [78]. Key factors explaining the high number of publications: (1) Research on drinking water is increasing significantly in low- and lower-middle-income countries. In particular, in regard to published research on this subject, India has outdone the United States [23]. (2) Countries such as China have seen a nationwide spatial association between water quality and cancer, highlighting the importance of surface water quality in cancer incidence, and studies in China have focused on bladder and breast cancer, while India has seen research on esophageal cancer [28, 79]. (3) The patterns of collaboration currently in place indicate that established publishing giants such as the United States and the UK, which are known for producing large volumes of publications, are the main focus of partnerships [23].

The topic of ‘Assessing Drinking Water Quality and Health Risks from Contaminants’ was one of the main hot topics in the current study. The well-being of the general population is critically dependent on the safety of drinking water, as current studies show a relationship between water quality and the development of cancer risk. Examining the types of contaminants, their concentrations, and duration of exposure as well as performing health risk analyses to investigate the presence of pollutants and their possible cancer-causing ability constitute the main areas of focus [80, 81]. Monitoring activities include periodic studies for toxins, including pharmaceuticals and industrial chemicals, heavy metals (lead, arsenic, chromium), DBPs (chlorine reacting with organic matter to create cancer-causing trihalomethanes) and other pollutants [82, 83]. Maximum contamination levels (MCLs) are determined by scientific evidence; regulations are then enforced to ensure that water treatment facilities maintain pollution levels below these thresholds [84–86]. Ongoing studies are being conducted to assess the frequency and concentration of pollutants in various water supplies. Research is being conducted to identify high-risk areas and investigate particular health effects, such as cancer, generated by these pollutants. The ultimate objective is to improve risk assessments and to provide useful data for legislative development. All creatures depend on access to drinkable water and sanitation; however, poor socioeconomic conditions and rapid changes in land use have degraded the quality and availability of water, therefore affecting human health. Officially, the United Nations (UN) acknowledges that every human being has many fundamental rights, including the right to safe drinking water [87]. Global accessibility to safely managed drinking water has continually improved, growing from 625 in 2000 to 74% in 2020. Despite this progress, nearly 2 billion people do not have access to safely managed drinking water, including 771 million who lack even basic water services [88]. Efforts to ensure water accessibility and quality are essential for long-term human health [89].

Another subject that has received much attention is “Experimental Research on Carcinogenic Effects of Chemicals in Drinking Water Using Animal and Human Models". A major focus of environmental health studies is the search for possible carcinogens in drinking water [90–92]. Using a thorough approach, researchers have examined the carcinogenic effects of these chemicals by means of animal models and experiments with human subjects [93, 94]. Research aims to clarify the exact molecular and cellular pathways by which these chemicals might cause cancer. Clarifying the changes in gene expression caused by these pollutants is highly important. This analytical approach clarifies possible routes involved in carcinogenesis, especially by emphasizing genes responsible for programmed cell death, DNA repair mechanisms, and cellular proliferation. Moreover, scientists have investigated the processes by which toxins induce uncontrollably rapid cellular division, supporting the development of tumors [95, 96]. Furthermore, there has been a deliberate attempt to investigate the relationship between environmental toxins and the frequency of chronic inflammation, a known precursor of cancer [97, 98]. To study their effects on tumor development, animal models, such as mice and rats, are purposely exposed to particular chemicals, providing a detailed analysis of these mechanisms. Concurrent with this, there are epidemiological studies including human populations. These studies track cancer incidence among drinking water with different degrees of pollutants. This complementary approach helps to create links between particular chemicals and cancer risk, enabling a more complete knowledge of environmental health hazards.

A thematic analysis of highly cited papers in scientific literature on drinking water and its possible connection with cancer reveals a concentrated study of subtopics closely related to established areas of research. This observation points to increasing scholarly attention in this field and more intense interest in recent years. In particular, the most cited paper, written by Järup L. and published in the British Medical Bulletin in 2003 [61], has almost 4,728 citations. This study highlighted how exposure to lead, cadmium, mercury, and arsenic causes major human health hazards related to heavy metals. These metals have been well investigated, and international agencies such as the World Health Organization (WHO) routinely evaluate how they affect human health. Human use of heavy metals goes back millennia. Although several negative health effects associated with these metals are well known, exposure to these metals continues and may even increase in some areas of the world, especially in less developed nations. On the other hand, in most developed countries in recent years, emissions have decreased [99].

The second most frequently cited study [47] was published in Mutation Research—Reviews in Mutation Research. This review thoroughly evaluated the occurrence, genotoxicity, and carcinogenic potential of DBPs in drinking water. It investigated comprehensively the formation of DBPs resulting from the interaction of disinfectants—such as chlorine, ozone, chlorine dioxide, or chloramines—with naturally occurring organic matter, human-made pollutants, bromide, and iodide during the drinking water disinfection process. That fundamental work covered three decades of research, encompassing a wider spectrum of DBPs. It specifically investigated the occurrence, genotoxic characteristics, and carcinogenic potential of 85 DBPs, including 74 newly discovered DBPs based on their presence and possible toxicological effects, as well as 11 DBPs currently under the U.S. Environmental Protection Agency (EPA) regulation.

Strengths and limitations

This study focused on a unique examination of the research landscape surrounding drinking water and its potential association with cancer. Recognizing the importance of international collaboration, we observed a notable increase in the volume of published research on this topic. However, the limitations inherent to the chosen database (Scopus) restrict the comprehensiveness of our findings. Although Scopus offers extensive coverage across disciplines, it excludes certain peer-reviewed journals, particularly those originating from Asia and Africa, regions where drinking water pollution poses a significant public health challenge. These excluded journals are primarily located in India, China, Indonesia, the Middle East, and other Asian and African nations. Consequently, our analysis omits publications found within these unindexed journals.

Despite the implementation of a rigorous search strategy, our study shares the inherent limitations of bibliometric analyses. The possibility of false positives and false negatives cannot be entirely eliminated. Additionally, our reliance on Scopus data for identifying active research institutions and funding agencies introduces potential biases. Inconsistencies in the way institutions are named across different publications can skew the research output and subsequent rankings generated from our analysis. This issue extends to funding agencies, as name changes can influence their visibility and evaluation. In particular, our search strategy aimed to minimize false positives by restricting relevant keywords to abstracts and titles, focusing exclusively on studies directly related to our area of interest (drinking water and cancer).

Although a list of highly cited articles has been compiled, it is crucial to acknowledge the limitations of citation counts as a sole measure of research impact. Self-citation and other factors can significantly distort these metrics. It is therefore possible that our review of highly cited articles may have inadvertently overlooked influential and established contributions to the field.

Conclusions

A bibliometric analysis was performed to investigate publication trends in global research on drinking water-related cancer between 1993 and 2023. This approach examined publication volume, publication types, and prominent research themes. The analysis revealed that original research articles constituted the dominant type of publication within the field. In particular, the number of publications on drinking water-related cancer has increased significantly over the past decades. The United States and China emerged as the most prolific contributors to this research area. Two primary research themes emerged as central areas of investigation: "Assessing Drinking Water Quality and Health Risks from Contaminants" and "Experimental Research on Carcinogenic Effects of Chemicals in Drinking Water Using Animal and Human Models." This study has significant implications for policymakers by pinpointing areas that warrant increased investment and research funding. By strategically targeting relevant environmental sectors, this knowledge can ultimately contribute to improving global drinking water safety. To advance our understanding and develop effective strategies, further research is essential. This includes improving methods for detecting and measuring emerging contaminants, as well as evaluating the impact of water treatment and sanitation practices.

Acknowledgements

The authors would like to thank Palestine Technical University (Kadoorie) and An-Najah National University for all administrative assistance during the project’s implementation.

Author contributions

SH.Z. and S.H.Z. initiated the study, designed, and performed the analysis, interpreted the data, and wrote the main paper. All authors read and approved the final manuscript.

Funding

Not applicable.

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This analysis is without human involvement. There was no need for ethical approval.

Consent for publication

Not applicable.

Competing interests

The author declares that they have no competing interests.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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