Environmental Toxicants and Colorectal Cancer

Wooden basket full of varied fresh vegetables on dark table symbolizing that a nutrient-dense diet may help reduce colorectal cancer risk.
                                                                                                                                                                                                                   Read Time: 6 Minutes

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths worldwide,1 and incidence of early-onset CRC continues to increase in the US and other industrialized countries.2 Younger patients diagnosed with CRC often present with advanced disease, which has led to an increase in CRC-related deaths in patients under 50 years of age.3 Recent US reporting also indicates that CRC incidence, survival, and mortality vary substantially by race and ethnicity.4 In addition to genetic predisposition, several lifestyle-based factors have been associated with an increased risk of developing CRC, from increased alcohol intake and sedentary behaviors to decreased fiber and plant consumption and physical activity levels.5,6

Research studies also suggest connections between some environmental pollutants and CRC risk. How can a functional medicine approach and lifestyle modification help to reduce chronic toxicant exposures, enhance the body’s biotransformation and detoxification pathways, and help to reduce the risk of CRC development?

Pollutants and CRC: From Pesticides to Particulates

Studies continue to investigate whether environmental toxicant exposures elevate the risk of CRC. Recent research investigating links between pesticide exposures and CRC have not shown definitive associations; however, results suggest that some of these chemicals may play a role.7 A 2021 systematic review examined pesticide exposures and CRC risk, evaluating 139 studies that included participant populations such as farmers, pesticide manufacturers, people in rural communities, and those who consumed foods with pesticide residues.8 While overall results showed a similar number of significant positive and inverse associations, researchers identified specific pesticides that are legally used in the US that were also associated with an elevated colon, rectal, or colorectal cancer risk such as terbufos, dicamba, trifluralin, S-ethyl dipropylthiocarbamate (EPTC), imazethapyr, chlorpyrifos, carbaryl, pendimethalin, and acetochlor.8

Hazardous chemical exposures, including asbestos,9 industrial complex pollutants,10 and air pollution particulates11 may also increase the risk of CRC development. A 2022 meta-analysis investigating links between outdoor particulate matter (PM) air pollution and increased risks of gastrointestinal cancers found that exposure to PM2.5 was associated with a 12% increased risk of gastrointestinal cancer overall and a 35% increased risk of colorectal cancer.11 Due to limitations in the analysis, researchers were not able to determine if the elevated cancer risks were due to acute or chronic exposures.

EDCs in Personal Care Products & CRC Risk

Chemical ingredients present in some personal care products have been identified as endocrine-disrupting chemicals (EDCs) and have been associated with an increased risk of various cancers.12,13 Specific to colon and rectal cancers, a human cell study determined that the EDC bisphenol A (BPA) promoted the proliferation, migration, and tumor growth of colon cancer cells in both in vitro and in vivo evaluations.14 Other EDCs commonly used in personal care products, such as phthalates, have been associated with CRC risk. A 2021 study (n=221) compared the concentrations of urinary phthalate metabolites between healthy participants, patients with colorectal adenomas, and patients with CRC.15 Study results indicated a significantly higher urinary phthalate metabolite concentration in patients with CRC compared to patients with adenoma or healthy individuals.15 Researchers concluded that higher exposure levels to phthalates may contribute to CRC incidence.15

Recently, a mouse model was used to study another chemical frequently seen in common personal care products, triclocarban.16 Low-dose exposure to this chemical, which has similar properties to the EDC triclosan,17 was found to increase the severity of colitis and promote the development of colitis-associated colon cancer through gut microbiota mechanisms.16

Health Inequities in Cancer Risk, Diagnosis, and Access to Treatments

Studies continue to report that hazardous chemical exposures from sources such as industrial pollutants and personal care products disproportionately impact communities of color.18-21 For example, a 2020 observational study (n=46,709 women; ages 35-74) found that compared to non-use, permanent hair dye use was associated with a 45% higher breast cancer risk in Black women (CI: 1.10-1.90) and a 7% higher risk in white women (CI: 0.99-1.16).22 In addition to breast cancer, research continues to highlight racial health inequities in risk, diagnosis, and care for a variety of cancers, from lung and thyroid cancers to leukemia.23-26 In fact, the American Society of Clinical Oncology (ASCO) recently reported on treatment inequities for cancers such as leukemia and lymphoma that often use bone marrow transplants.27 According to the ASCO, due to a lack of ethnic and racial diversity in the volunteer bone marrow donor registry, a white patient has a 77% chance of finding a bone marrow match while a Black person only has a 23% chance of finding a matched donor. Asian and Pacific Islander patients have a 41% chance, Hispanic or Latino patients have a 46% chance, and American Indian and Alaska Native (AIAN) patients have a 57% chance of finding a matched donor.27

Regarding colorectal cancer, incidence, survival, and mortality rates vary substantially in the US by race and ethnicity, with the highest incidence and mortality among AIAN and non-Hispanic Black individuals.4 As an example, CRC mortality rates are 46% higher in AIAN men and 44% higher in Black men compared to white men. In addition, Black individuals are more likely to be diagnosed with metastatic CRC (25%) compared to white individuals (21%), and Black individuals are less likely to receive either timely follow-up after a positive stool test or a high-quality colonoscopy.4 Recent reporting has also emphasized the growing inequity in early-onset CRC reflected by steep diagnosis increases among indigenous Alaskans, growing from 18.8 cases per 100,000 individuals aged 20 to 49 years during 1998 through 2002 to 34.8 cases per 100,000 during 2014 through 2018.28

Lifestyle-Based Approaches to Health and Reducing CRC Risk

Due to the potential increased CRC risk associated with some environmental toxicants, reducing levels of exposure while supporting the body’s detoxification and elimination pathways are possible health strategies. In the functional medicine model, assessment of a patient’s total toxic load and recognizing ongoing exposures are essential pieces of personalized therapeutic treatments. The Toxin Exposure Questionnaire is a tool within the extensive IFM Toolkit, available to IFM members, that tracks a patient’s vulnerability to harmful chemicals and the progress of therapeutic interventions. In addition, optimizing a patient’s nutritional status, ensuring adequate fiber and water intake, eating more phytonutrient-dense and diverse foods, and supporting liver function through targeted, nutrient-dense diets such as IFM’s Detox Therapeutic Food Plan are all dietary treatment approaches within the functional medicine model that may help to improve the elimination of toxic compounds and to alleviate toxic burden.

Preventative CRC screenings as well as nutrient-dense diets high in fruit, vegetables, and whole grains and low in animal fats have been recommended for reducing risk of colon and rectum cancers.29 A recent meta-analysis of 49 observational studies (n=3,059,009 total participants) found that a plant-based diet significantly reduced the risk of colorectal, rectal, and colon cancers by 24%, 16%, and 12%, respectively.30 In addition, a 2022 meta-analysis found that increasing soluble and insoluble fiber consumption was protective against CRC.31 Other studies have evaluated the impact of specific nutrients on CRC risk. A 2022 case-control study (n=207 CRC cases and 220 controls) suggested that consumption of dietary antioxidants such as vitamins A, C, E, zinc, selenium, and manganese from a high-quality diet may significantly reduce odds of CRC incidence.32 Further, a 2023 meta-analysis of 28 observational studies found an inverse association between circulating vitamin D levels and CRC risk, ranging from a 20 to 39% reduced risk.33

At IFM’s Environmental Health Advanced Practice Module (APM), learn more about how your patient’s physical environment and toxicant exposure levels may impact their health outcomes and what lifestyle-based tools may benefit their wellness path.

Learn More About Biotransformation Pathways and Toxic Exposures

Related Articles

Colorectal Cancer: Disease Risk and Prevention

Common Endocrine-Disrupting Chemicals and Women’s Health

Exposure to Pesticides, Herbicides, & Insecticides: Human Health Effects

Neighborhood Health: Pollutant Exposures & Chronic Disease Risk

Supporting Liver Function With Nutrition

  1. World Health Organization. Colorectal cancer. Published July 11, 2023. Accessed September 26, 2023.
  2. Sinicrope FA. Increasing incidence of early-onset colorectal cancer. N Engl J Med. 2022;386(16):1547-1558. doi:1056/nejmra2200869
  3. Cheng E, Blackburn HN, Ng K, et al. Analysis of survival among adults with early-onset colorectal cancer in the National Cancer Database. JAMA Netw Open. 2021;4(6):e2112539. doi:1001/jamanetworkopen.2021.12539
  4. Siegel RL, Wagle NS, Cercek A, Smith RA, Jemal A. Colorectal cancer statistics, 2023. CA Cancer J Clin. 2023;73(3):233-254. doi:3322/caac.21772
  5. Song M, Chan AT, Sun J. Influence of the gut microbiome, diet, and environment on risk of colorectal cancer. Gastroenterology. 2020;158(2):322-340. doi:1053/j.gastro.2019.06.048
  6. O’Sullivan DE, Sutherland RL, Town S, et al. Risk factors for early-onset colorectal cancer: a systematic review and meta-analysis. Clin Gastroenterol Hepatol. 2022;20(6):1229-1240.e5. doi:1016/j.cgh.2021.01.037
  7. Su LJ, Young SG, Collins J, Matich E, Hsu PC, Chiang TC. Geospatial assessment of pesticide concentration in ambient air and colorectal cancer incidence in Arkansas, 2013-2017. Int J Environ Res Public Health. 2022;19(6):3258. doi:3390/ijerph19063258
  8. Matich EK, Laryea JA, Seely KA, Stahr S, Su LJ, Hsu PC. Association between pesticide exposure and colorectal cancer risk and incidence: a systematic review. Ecotoxicol Environ Saf. 2021;219:112327. doi:1016/j.ecoenv.2021.112327
  9. Kwak K, Paek D, Zoh KE. Exposure to asbestos and the risk of colorectal cancer mortality: a systematic review and meta-analysis. Occup Environ Med. 2019;76(11):861-871. doi:1136/oemed-2019-105735
  10. García-Pérez J, Fernández de Larrea-Baz N, Lope V, et al. Residential proximity to industrial pollution sources and colorectal cancer risk: a multicase-control study (MCC-Spain). Environ Int. 2020;144:106055. doi:1016/j.envint.2020.106055
  11. Pritchett N, Spangler EC, Gray GM, et al. Exposure to outdoor particulate matter air pollution and risk of gastrointestinal cancers in adults: a systematic review and meta-analysis of epidemiologic evidence. Environ Health Perspect. 2022;130(3):36001. doi:1289/ehp9620
  12. Chang CJ, O’Brien KM, Keil AP, et al. Use of straighteners and other hair products and incident uterine cancer. J Natl Cancer Inst. 2022;114(12):1636-1645. doi:1093/jnci/djac165
  13. Qin L, Deng HY, Chen SJ, Wei W. A meta-analysis on the relationship between hair dye and the incidence of non-Hodgkin’s lymphoma. Med Princ Pract. 2019;28(3):222-230. doi:1159/000496447
  14. Jun JH, Oh JE, Shim JK, Kwak YL, Cho JS. Effects of bisphenol A on the proliferation, migration, and tumor growth of colon cancer cells: in vitro and in vivo evaluation with mechanistic insights related to ERK and 5-HT3. Food Chem Toxicol. 2021;158:112662. doi:1016/j.fct.2021.112662
  15. Su WC, Tsai YC, Chang TK, et al. Correlations between urinary monoethylhexyl phthalate concentration in healthy individuals, individuals with colorectal adenomas, and individuals with colorectal cancer. J Agric Food Chem. 2021;69(25):7127-7136. doi:1021/acs.jafc.1c00953
  16. Yang H, Sanidad KZ, Wang W, et al. Triclocarban exposure exaggerates colitis and colon tumorigenesis: roles of gut microbiota involved. Gut Microbes. 2020;12(1):1690364. doi:1080/19490976.2019.1690364
  17. Halden RU, Lindeman AE, Aiello AE, et al. The Florence Statement on triclosan and triclocarban. Environ Health Perspect. 2017;125(6):064501. doi:1289/EHP1788
  18. Hii M, Beyer K, Namin S, Malecki K, Rublee C. Respiratory function and racial health disparities with residential proximity to coal power plants in Wisconsin. WMJ. 2022;121(2):94-105.
  19. US Environmental Protection Agency Office of Land and Emergency Management. Population surrounding 1,857 Superfund remedial sites. Environmental Protection Agency. Updated September 2020. Accessed September 27, 2023.
  20. American Lung Association. State of the Air 2023: key findings. American Lung Association. Published 2023. Accessed July 26, 2023.
  21. Johnson PI, Favela K, Jarin J, et al. Chemicals of concern in personal care products used by women of color in three communities of California. J Expo Sci Environ Epidemiol. 2022;32(6):864-876. doi:1038/s41370-022-00485-y
  22. Eberle CE, Sandler DP, Taylor KW, White AJ. Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women. Int J Cancer. 2020;147(2):383-391. doi:1002/ijc.32738
  23. Lee RJ, Madan RA, Kim J, Posadas EM, Yu EY. Disparities in cancer care and the Asian American population. Oncologist. 2021;26(6):453-460. doi:1002/onco.13748
  24. Harrison S, Judd J, Chin S, Ragin C. Disparities in lung cancer treatment. Curr Oncol Rep. 2022;24(2):241-248. doi:1007/s11912-022-01193-4
  25. Chen DW, Yeh MW. Disparities in thyroid care. Endocrinol Metab Clin North Am. 2022;51(2):229-241. doi:1016/j.ecl.2021.11.017
  26. Zavala VA, Bracci PM, Carethers JM, et al. Cancer health disparities in racial/ethnic minorities in the United States. Br J Cancer. 2021;124(2):315-332. doi:1038/s41416-020-01038-6
  27. American Society of Clinical Oncology. Why the bone marrow registry needs more diverse donors and how to sign up. Published March 30, 2021. Accessed September 27, 2023.
  28. Kratzer TB, Jemal A, Miller KD, et al. Cancer statistics for American Indian and Alaska Native individuals, 2022: including increasing disparities in early onset colorectal cancer. CA Cancer J Clin. 2023;73(2):120-146. doi:3322/caac.21757
  29. Division of Cancer Prevention and Control. What can I do to reduce my risk of colorectal cancer? Centers for Disease Control and Prevention. Reviewed February 23, 2023. Accessed September 26, 2023.
  30. Zhao Y, Zhan J, Wang Y, Wang D. The relationship between plant-based diet and risk of digestive system cancers: a meta-analysis based on 3,059,009 subjects. Front Public Health. 2022;10:892153. doi:3389/fpubh.2022.892153
  31. Arayici ME, Mert-Ozupek N, Yalcin F, Basbinar Y, Ellidokuz H. Soluble and insoluble dietary fiber consumption and colorectal cancer risk: a systematic review and meta-analysis. Nutr Cancer. 2022;74(7):2412-2425. doi:1080/01635581.2021.2008990
  32. Vahid F, Rahmani W, Davoodi SH. The association between dietary total antioxidant capacity and quality of nutrients with odds of colorectal cancer: a hospital-based case-control study. Clin Nutr ESPEN. 2022;52:277-284. doi:1016/j.clnesp.2022.09.007
  33. Hernández-Alonso P, Boughanem H, Canudas S, et al. Circulating vitamin D levels and colorectal cancer risk: a meta-analysis and systematic review of case-control and prospective cohort studies. Crit Rev Food Sci Nutr. 2023;63(1):1-17. doi:1080/10408398.2021.1939649

Related Insights