Environmental and Occupational Exposures

Air Pollution

Particulate matter [ PM2.5 ] and other pollutants such as nitrogen dioxide and sulfur dioxide are established carcinogens. Urbanization and industrialization have dramatically increased air pollution exposure, especially in countries like India and China.

Air pollution increases risk of:

• Lung cancer (strongest evidence)
• Bladder cancer
• Possibly breast and other cancers (in research stage)

Chemical Exposures

Exposure to pesticides, industrial solvents, heavy metals, endocrine disrupting chemicals, and microplastics has expanded significantly in recent decades.

Though evidence varies by substance, many chemicals are known or suspected carcinogens. Long term, low level exposure in food, water, and consumer products contributes to cumulative risk.

Occupational Hazards

Workers in industries involving asbestos, benzene, silica dust, diesel exhaust, and radiation have higher incidence of specific cancers. Despite improved regulations in many countries, occupational risks remain high in developing regions.

Infectious Causes of Cancer

Infections account for a large proportion of cancers worldwide. While some of these are declining due to vaccination and better sanitation, others remain widespread or newly recognized.

HPV [ Human Papillomavirus ]

HPV causes:

• Cervical cancer
• Anal cancer
• Oropharyngeal cancer
• Penile and vaginal cancers

In countries with low HPV vaccination coverage, cervical cancer continues to rise in absolute numbers due to population growth.

HPV driven oropharyngeal cancers are increasing in many Western countries due to changes in sexual behaviors.

Hepatitis B and C

Chronic HBV and HCV infections lead to liver cancer. While vaccination has reduced HBV transmission in some regions, liver cancer remains a major contributor to global incidence, especially in Asia and Africa.

Helicobacter pylori

H. pylori is strongly associated with gastric cancer. Despite improved sanitation reducing infection prevalence, gastric cancer remains widespread, especially in East Asia.

HIV and Immunosuppression

Immunosuppression increases risk of Kaposi sarcoma, lymphomas, and HPV related cancers. With more people living long term with HIV thanks to antiretroviral therapy, we are seeing shifts in incidence patterns of these cancers.

Medical advances in Diagnostics, Screening    

A critical, often misunderstood, factor in rising cancer incidence is better detection.

Improved Diagnostic Technologies

Modern imaging such as MRI, CT scans, ultrasound, PET scans, and endoscopy detects cancers earlier and more often. Many cancers that previously went unnoticed until very advanced stages are now diagnosed in early stages or even incidentally.

Screening Programs

Population level screening has increased detection rates for:

• Breast cancer (mammography)
• Cervical cancer (Pap smear, HPV testing)
• Colorectal cancer (colonoscopy)
• Prostate cancer (PSA testing)
• Lung cancer in high-risk populations

While screening saves lives, it also increases incidence statistics by identifying cancers earlier and detecting lesions that may never have progressed–overdiagnosis.

Overdiagnosis

Overdiagnosis means diagnosing cancers that would not have caused harm during a patient’s lifetime. This contributes to the steep rise in incidence for:

• Thyroid cancer
• Prostate cancer
• Some breast cancers
• Early stage lung cancers in heavily screened populations

This phenomenon has become very pronounced with the widespread use of high resolution imaging.

Better Cancer Registries

Many countries have improved cancer registration and reporting systems. As registries become more complete and accurate, recorded incidence rises even if true incidence has not changed dramatically.

Genetic and Biological Factors

Genetic Predisposition

A small but significant proportion of cancers arise from inherited mutations:

• BRCA1/BRCA2 (breast, ovarian)
• Lynch syndrome (colorectal, endometrial)
• TP53 (Li-Fraumeni syndrome)
• APC (familial adenomatous polyposis)

Better genetic testing means more hereditary cancers are identified today than in the past.

Epigenetic Changes

Modern exposures and lifestyle factors influence gene expression and cancer risk through:

• DNA methylation
• Histone modification
• Non-coding RNAs

Chronic inflammation, obesity, infections, and environmental toxins all contribute to epigenetic dysregulation.

Microbiome Changes

The gut microbiome plays a role in immunity, metabolism, inflammation, and carcinogenesis. Diets high in processed foods, low in fiber, and widespread antibiotic use have altered microbial ecosystems, increasing risk for colorectal and other cancers.