Childhood cancers are a rising global concern. Many studies have attempted to look at the risk factors that increase risk the off of cancer in the pediatric population. Similar to other research on risk factors for childhood cancers, this study revealed that a number of sociodemographic, socioenocmic, genetic and environmental risk factors that are associated with cancers in children.
Some of the sociodemographic and socioeconomic risk factors examined in this study and were consanguinity between parents, education level of both parents and the occupation of both parents. Consanguineous marriages have long been associated with an increased risk for a number of diseases such as autosomal recessive diseases and congenital malformations.19 Additionally studies shown that in some Arab communities where there is a high rate of consanguinity, there is a significant increase in the prevalence of common non-communicable diseases like cancer.20 This directly correlates to the findings of this study, which showed that consanguinity of parents significantly increases odds of cancer in their children. In addition, education level of the parents and its correlation to cancer incidence in their children has been the topic of debate in the past decade. Yet most studies looked at the correlation between the educational level of the parents and the child’s cancer survival rate, whereby children whose parents had higher education (University) had a slightly significantly better survival rate.21 These studies emphasized that the education level of the mother is more important than education level of the father.21,22 Very few studies looked at the relationship between the education level of the parents and the risk of cancer in her children. From these, few studies it was revealed that the children of parents with lower level of education had a slightly increased risk of cancer.23 Correspondingly, this was also observed in this study. The occupation of the mother has been thoroughly studied in order to determine if there is an association between a mother’s occupation and an increased risk of cancer in her children. It has been hypothesized that a mother occupational exposure to certain chemical such as petroleum, solvents that contain chlorinated hydrocarbons, paints, and pesticides might affect childhood cancer in the offspring through genetic changes in the ovum and/or through trans-placental carcinogenesis.24,25 In this study, the majority of the mothers were homemakers as such they are less likely to be exposed to the aforementioned chemicals and solvent, yet the occupation of the mother was shown to significantly increase the odds of her children developing cancer. Nevertheless, it should be noted that this association maybe due to confounders that were unmeasured and unaccounted for in our study such as family income, access to quality of pre-natal healthcare services etc. On the other hand the result of this study showed that a father’s occupation did not significantly increase odds of cancer in his children. There is inconsistent data on this issue; however some studies were able to associate certain types of paternal occupational exposure such as exposure to radioactive material, lead, asbestos, cadmium etc., with an increased risk of cancer in his children. 25, 26,27
Environmental risk factors that were examined in this study were area of residence (urban vs. rural), and if living in proximity to high-voltage electrical networks, garbage disposal areas, industrial factories and highways or not. Existing literature suggests modest yet positive associations between urbanization and residential area and cancer incidence in all age population. 28 This is may be due to the high levels of air pollution in urban areas and exposure to all sorts of pollutants, chemicals etc. In this study, children who lived in urban and suburban areas were shown to have significantly higher odds of cancer. However, studies have shown that people of all age groups and specifically children living in urban areas are more likely to be screened for and diagnosed with cancer due to the fact that access to healthcare services in urban areas is much easier than in rural areas. 29,30 This is the case in Lebanon where the healthcare system is highly fragmented, the private healthcare sector is dominant and the vast majority of healthcare institutions are located in urban areas namely the Greater Beirut Area.31 Whereas in rural areas there are a limited number of healthcare facilities, most of them public and are unable to meet the health needs of the population living in those rural areas.32
Several studies have examined association between childhood cancers and living near high-voltage electrical networks, but no consistent evidence for an association between living near high-voltage electrical networks (or any source of non-ionizing Electromagnetic fields (EMF)) and cancer has been found.33 Nevertheless, our results show that children living near high-voltage electrical networks have higher odds of developing cancer.
Results of this study suggest that children who lived in proximity to industrial factories were at higher odds of cancer as opposed to those who did not. Similarly, the literature suggests a possible positive association between living in proximity to certain industrial factories and risk of childhood cancer34 ; however, more studies are necessary before establishing and confirming this relationship. Moreover, our findings show that children who lived in proximity to highways were at higher odds of cancer as opposed to those who lived far from highways (more than 500 meters). Likewise, reported studies show that children living in proximity of highways are exposed to higher concentrations of traffic-related carcinogenic pollutants and in turn they have an increased risk of childhood cancer, but the published evidence remains inconclusive. 35,36
Possible associations between certain types of cancer such as for liver cancer, kidney cancer, pancreatic cancer, and non-Hodgkin’s lymphomas and living close to garbage disposal sites/landfills have been studied yet the evidence is inconsistent.37,38,39 In addition most of the studies on this subject looked the association between living close to garbage disposal sites/landfills and risk of cancer in adults (and not in children). 40 The finding of this study children living in garbage disposal areas/landfills are at higher odds of developing cancer. It should be noted that since 2015 Lebanon has been witnessing a waste management crisis with widespread dumping and burning of garbage/waste on the streets.41,42 Human Rights Watch calls this crisis "a national health crisis".42 Studies conducted by local research and environmentalists shows that there has been increase in cancer rates in the past couple of years in the Lebanese population at large as a results of the exposure garbage/waste on the streets that been dumped and burned on the streets since 2015.43,44
Lastly, this study looked at genetic risk factors such as were studied history of malignancy in parents, history of malignancy in siblings and history of malignancies in second degree family. Most cancers are not clearly linked to genetics and family history. However, certain types of cancer such as breast cancer, ovarian cancer, uterine cancer, colorectal cancer, melanoma, retinoblastoma and pancreatic cancer have been shown to run in some families.45,46 In a study published in the New England Journal of Medicine, 8.5% of the children (below age of 18) with cancer were found to have germ line mutations in cancer-predisposing genes.15 The results of this study highlighted that sibling history of cancer significantly led to higher odds of cancer in children, but that history of cancer in both parents did not significantly increase odds of cancer in their children. This was also the case when it comes to history of malignancies in paternal and maternal second-degree family members (aunts, uncles, cousins etc.).
Study strength and limitations
Strengths
This study was the first of its kind in Lebanon to our knowledge. That being so the findings of this study can be used in future studies on the risk factors of childhood cancer in Lebanon and even in other low to middle income countries in the Eastern Mediterranean Region (EMR). Accordingly, this study can be a starting point to conducting a large wider scale study that examines a wider range of sociodemographic, socioeconomic, environmental and genetic risk factors risk factors for developing a childhood cancer. Additionally, the developed questionnaire can be used in future studies as it has been validated and translated to Arabic.
Limitations
Since this study is a cross-sectional one, it has some limitations including; it only offers a snapshot of a single point in time and thus is not appropriate to establish causality between the different risk factors for childhood cancers. Additionally, recall bias might be a major drawback whereby participants do not remember previous events or experiences accurately or omit details (consciously or unconsciously). Recall bias can increase or decrease the strength of the observed associations. Overestimation of risk estimates due to recall bias is of concern particularly in studies of parental self-reporting of sociodemographic factors, children’s exposures to infections, chemicals etc. and childhood cancer.47,48 Furthermore, this study was limited to four privately owned tertiary hospitals located in the Greater Beirut Area. Finally, a significant limitation of this study is that analysis of the relationship between the aforementioned risk factors could not be performed to determine its association to specific subtypes of childhood cancers.
Areas for Future Research
Longitudinal studies that assesses the impact of risk factors such as sociodemographic socioeconomic, social, genetic as well other social determinants of disease on the health of children particularly with regards to risk of malignancies and cancers are highly warranted. Thus, for future research, it is recommended that similar studies to be carried out across all 130 hospitals; both public and private in urban as well as in rural areas; across all the areas of Lebanon in order to obtain large sample sizes which will allow generalization of results on a national and regional level.
Policy implications
The results of this study helps health policy makers and all governmental entities including (but not limited to) Ministry of Public Health, Ministry of Social Affairs, Ministry of Labor etc. identify public health policy priorities. This study supports the need to improve access to healthcare services in rural areas, promote effective urban planning that takes into consideration placing hazardous elements such as industrial factories, high-voltage electoral network etc. away from populated residence areas and promote early and correct diagnosis of childhood cancer especially for children who lie in the high risk population (lower socioeconomic) particularly those who have a family (and sibling) history of cancer.