To maintain freshness, the chemical formalin is extensively used for fruits, fish, and vegetables. Formalin-treated foods are openly sold in markets in less-developed countries, especially Bangladesh. Ingesting these foods may cause different types of cancer, predominantly lung cancer [15]. Smoking, tobacco use, previous history of lung disease such as asthma or tuberculosis, and genetic factors are the key factors in the development of lung cancer [16]. Polymorphic changes in the MDM2 gene have been identified as another reason for lung cancer, based on data collected from more than 11,638 patients [17]. Age is another important parameter. People older than 65 years of age are significantly affected compared to younger people in less-developed countries. It was reported that about 5887 lung cancer patients were admitted to the hospital in 2020, especially the National Institute of Cancer Research and Hospital (NICRH). Experts have suggested that smoking and air pollution are the main reasons for lung carcinoma [18]. Family income, area of residence, education status, and marital status are the four most common contributing factors in lung cancer, mainly for men older than 55 [19].

Hepatocellular carcinoma (HCC), i.e., liver cancer, is the third most common cancer, behind lung and gastric carcinoma [25]. About 8 million people in Bangladesh are infected with chronic hepatitis B or C virus. This can proceed to HCC, and recently non-alcoholic fatty liver disease (NAFLD) has been shown to increase the trend toward liver cancer [26,27]. For the manufacturing and processing of sutki (the local name for dried fish), dichlorodiphenyltrichloroethane (DDT) is commonly used, although it is banned by the government. This is also responsible for liver cancer [15].

Female gender, age, obesity, menarche (under 12 years of age), and radiation therapy to the chest or breasts are the main factors for breast cancer (BC) development [32,33,34]. One prevalent major risk factor among women was found to be overweight. In addition, menarche, contact with radiation to the chest or face, and age under 40 years were identified as major risk factors among Bangladeshi women. Family history is also a predominant factor in breast cancer [35]. The tendency to avoid breastfeeding and the changing reproductive system may increase the risk of breast cancer [36]. With the lack of accessibility to a hospital and the cost of diagnosis, many women are unwilling to seek a diagnosis due to their socio-economic status. Improper treatment, poverty, and late diagnosis are also contributing factors [37,38]. A report published by NICRH indicated that illiterate housewives were highly prone to be affected by breast cancer. Women living in urban areas are different from women in rural areas in their reproductive behavior; they are reluctant to marry, have children, or breastfeed [39]. The use of chemicals in dermatological products and crop production and bisphenol A in plastic materials is changing the secretion of estrogen, also leading to breast cancer development [38].

In less-developed countries, the most common gynecological cancer is cervical cancer [44], which is one of the leading causes of cancer death of women in Bangladesh. More than 50 million women are at risk for cervical cancer, with 17,686 cases diagnosed and 10,362 deaths each year [45]. Factors related to sex and reproduction are directly associated with cervical cancer, such as young age at the time of first sexual intercourse, multiple sexual partners, and unhygienic sex. Human papillomavirus (HPV) was also reported to be responsible for cervical cancer. The prevalence of cervical cancer in Bangladesh has been reported to be 25–30 per 100,000 women [46].

In less-developed countries, Helicobacter pylori (H. pylori) infection is high due to poor socioeconomic conditions [49] compared to Europe and the United States [50]. H. pylori causes noncardiac gastric carcinoma and low-grade B-cell mucosa-associated lymphoid tissue lymphoma (MALT) [51], but the vast majority is noncardiac gastric carcinoma [52]. H. pylori infection affects people based on age and sex, as well as salt intake, smoking, education, family income, and drinking water [53]. H. pylori is an important contributing factor in increasing gastric carcinoma and other gastric malignancies in Bangladesh [54].

According to the report, age as the main cause of prostate cancer applies to the 46-to-70-year-old group [11]. The rate of prostate cancer is higher for smokers than non-smokers in less-developed countries, especially in Bangladesh. While it has been difficult to identify the genetic causes of prostate cancer due to the lack of an accurate database, it is also difficult to obtain family histories due to illiteracy and the lack of proper screening in rural areas. However, it has been identified that family history plays a role in this cancer [11,58]. Polymorphic changes among two genes CDH1 (-160C/A) and Exo1 (K589E), have been identified as a crucial parameter for the development of prostate carcinoma, as reported in a study of 100 patients [12].