Silica fragments from millet bran in mucosa surrounding oesophageal tumours in patients in northern China

Exposure to silica and systemic sclerosis: A retrospective cohort study based on the Canadian Scleroderma Research Group

Introduction

Systemic sclerosis (SSc) is thought to be induced by an environmental trigger in genetically predisposed individuals. This study assessed the demographic and clinical characteristics and disease severity of silica exposed SSc patients.

Methods

Data was obtained from the Canadian Scleroderma Research Group (CSRG) cohort, containing 1,439 patients (2004–2019). Univariate and multivariate logistic regression analyses were performed, to determine the phenotype and severity of silica-exposed SSc patients. Mortality was assessed using Cox Survival Regression and Kaplan-Meier analyses.

Results

Among 1,439 patients (86.7% females), 95 patients reported exposure to silica. Those exposed were younger, of male sex and with more severe disease. Sex differences were observed where male patients exposed to silica were more likely to be Caucasian and smokers whereas female patients were younger at SSc diagnosis compared to unexposed. Multivariate regression, controlled for multiple confounders, showed that silica exposure was associated with a younger age at diagnosis and worse disease severity and mortality.

Conclusion

Exposure to silica was reported in ∼7% of CSRG cohort and ∼20% of male patients and was associated with a worse prognosis in terms of age of diagnosis, organ involvement and mortality. Hence, screening for silica exposure among higher risk individuals may be beneficial and these patients may require closer monitoring for systemic disease.

Polycyclic aromatic hydrocarbons (PAHs) and esophageal carcinoma in Handan-Xingtai district, North China: a preliminary study based on cancer risk assessment

Extremely high risk of esophageal carcinoma (EC) occurs in Handan-Xingtai district of North China. In spite of various preventive measures and epidemiological investigations that have been conducted for years, incidence and mortality of EC are still in the highest level of China. The etiology of EC remains unclear in the region. Previous studies of our research group proposed that polycyclic aromatic hydrocarbons (PAHs) that derived from numerous coal gangue dumps and atmospheric particulates were major contaminants in these regions. In consideration of mutagenic, teratogenic, and carcinogenic characteristics of PAHs, the authors hypothesized that severe exposure to PAHs could preform as a causative factor for EC. Therefore, four data sets documented in our previous studies were employed in this paper. To quantitatively evaluate the carcinogenic risk imposed by sixteen priority PAHs, incremental lifetime cancer risks (ILCRs) via three exposure pathways were calculated. The results showed that total ILCRs for adult group ranged from 2.08E-05 to 8.63E-02, with an average of 2.00E-02. Total ILCRs for childhood group ranged from 1.09E-05 to 4.48E-02, with an average of 1.04E-02. Total ILCR value of 94% samples exceeded 10^-4, indicating a particularly high carcinogenic risk to local residents. Furthermore, ingestion and dermal contact conducted as principal pathways of exposing to PAHs for each population group, rather than inhalation. It can be speculated that severely exposing to PAHs may be a pathogenesis of EC in Handan-Xingtai district. The rigorous supervise and governance are imperative to avoid severe exposure to PAHs that derived from coal gangue dumps.

Association of wheat chaff derived silica fiber and esophageal cancer in north China

BACKGROUND

Despite decades of research and intervention programs, the epidemic of esophageal squamous cell carcinoma (ESCC) in the Taihang Mountain area of north China has not seen convincing explanation by any risk factor yet and the incidence has not seen a substantial decrease. Based on recently disclosed association of aridity and wheat consumption with esophageal cancer, we revisited the hypothesis of biogenic silica in esophageal cancer development.

METHODS

From the archives of the Pathology Department of Heping Hospital, Changzhi Medical College, we selected three pairs of formalin-fixed samples, tumor tissues and distant normal tissues, of three patients operated for ESCC who had no history of workplace exposure to silica dust. Two pairs of dried tissue samples were used for phytolith (silica body) analysis and another pair for microanalysis with Transmission Electron Microscope (TEM).

RESULTS

One of the phytoliths in ESCC tumor tissue was similar to the prickle hair on the surface of wheat bract. In the mineral particles detected in the tumor tissue the predominant elements were Si, Ca, and P, whereas Si signals were not obvious in the distant normal tissue.

CONCLUSIONS

The preliminary findings on the detection of phytoliths and the higher than normal Si concentration in ESCC tumor tissue warrants further testing the role of biogenic silica in esophageal cancer.

A possible role of biogenic silica in esophageal cancer in North China?

Certain areas in North China have the highest incidence of esophageal squamous cell carcinoma (ESCC) in the world, which has not seen convincing explanation by any risk factor yet. Biogenic silica in millet bran was linked to ESCC in the early 1980s but the hypothesis was largely dismissed because of the lack of geographic correlation between millet consumption and ESCC. Later epidemiological studies disclosed the linkage of wheat consumption in North China to ESCC instead. Now, we hypothesize silica phytoliths (silicified bodies that have definite shapes) from wheat chaff are a major etiologic factor of ESCC in this region. This hypothesis is supported by the potentially high abundance of silica phytoliths on the bracts of wheat (Triticum aestivum) in North China due to favorable Si-accumulation genotype, arid climate, and siallitic soil with bioavailable Si. These silica phytoliths can contaminate wheat flour and cause repeated local injuries in the esophagus and stimulate proliferation by providing anchorage.

Systematic review: the etiology of esophageal squamous cell carcinoma in low-income settings

Esophageal carcinoma causes over 380 000 deaths per year, ranking sixth worldwide in mortality amongst all malignancies. Globally, the squamous cell subtype is most common and accounts for 80% of esophageal cancers. Nonetheless, esophageal squamous cell carcinoma is much more poorly understood than esophageal adenocarcinoma, including what is driving such high prevalences, why it often presents in young patients, and shows such marked geographical delineations Areas covered: The current literature was searched for articles focusing on aetiopathogenesis of squamous cell esophageal carcinoma via a systematic review, particularly in low-resource settings. This was supplemented by papers of interest known to the authors. Expert commentary: Current putative mechanisms include polycyclic aromatic hydrocarbons, nitrosamines, acetaldehyde, cyclo-oxygenase-2 pathways, androgen and their receptor levels, as well as smoking & alcohol, micronutrient deficiencies and diet, mycotoxins, thermal damage, oral hygiene and microbiotal factors, inhaled smoke, viral infections such as HPV, and chronic irritative states. Etiology is likely multifactorial and varies geographically. Though smoking and alcohol play a predominant role in high-income settings, there is strong evidence that mycotoxins, diet and temperature effects may play an under-recognized role in low and middle-income settings.

Extended phenotype in action. Two possible roles for silica needles in plants: not just injuring herbivores but also inserting pathogens into their tissues

Phytoliths are silica bodies of various shapes including in the shape of sharp needles formed by many land plants. Defense from herbivory is one of the several known functions of phytoliths, especially the mechanical defense by abrasion of the mouthparts of arthropods and the teeth of mammalian herbivores. Another, although somewhat lesser-known, anti-herbivory defensive mechanism of phytoliths is wounding by sharp silica needles. We discuss and illuminate an even much less known defensive mechanism by phytoliths, i.e., the ability of needle-like phytoliths to insert microscopic pathogens (bacteria, fungi, viruses) into herbivores' tissues. We do it by comparison and by showing analogy with the better-known insertion of microbial pathogens into the body of herbivores by thorns, spines, and prickles. This largely overlooked and understudied defensive mechanism is a special case of a double extended phenotype; plants' defense, and the multiplication and dispersal of microorganisms, and is thus a case of mutualism.

Five-year single-centre experience of carcinoma of the oesophagus from Blantyre, Malawi

Background

Oesophageal squamous cell carcinoma (OSCC) is increasing worldwide and has an exceptionally high prevalence in certain distinct geographical locations such as the African oesophageal SCC corridor. Despite this, there is a paucity of evidence to characterise the disease particularly in the Malawian context.

Method

We retrospectively audited our endoscopy database over 5 years, including for patient demographics, endoscopy findings, therapeutic intervention and recommendations for treatment.

Results

1586 patients with oesophageal cancer were identified from a total of 5882 endoscopy records from 2013 to 2017. Our cohort showed a larger proportion of oesophageal cancers found higher in the oesophagus compared with other African studies and a female preponderance in this upper-oesophagus disease subset though a male preponderance overall. 39% of patients with oesophageal cancer underwent bougie dilatation and 11% underwent palliative stent placement, which likely reflects local availability of resources.

Conclusion

This study validates the observation that OSCC predominates in sub-Saharan Africa in Malawi over other forms of oesophageal carcinoma, though our cohort appears to have subtly distinct demographics and disease-specific data. This highlights the need to prioritise preventative and therapeutic strategies for OSCC in this and similar settings.

Informing etiologic research priorities for squamous cell esophageal cancer in Africa: A review of setting-specific exposures to known and putative risk factors

Esophageal squamous cell carcinoma (ESCC) is one of the most common cancers in most Eastern and Southern African countries, but its etiology has been understudied to date. To inform its research agenda, we undertook a review to identify, of the ESCC risk factors which have been established or strongly suggested worldwide, those with a high prevalence or high exposure levels in any ESCC-affected African setting and the sources thereof. We found that for almost all ESCC risk factors known to date, including tobacco, alcohol, hot beverage consumption, nitrosamines and both inhaled and ingested PAHs, there is evidence of population groups with raised exposures, the sources of which vary greatly between cultures across the ESCC corridor. Research encompassing these risk factors is warranted and is likely to identify primary prevention strategies.

Silicotuberculosis with oesophagobronchial fistulas and broncholithiasis: a case report

A 76-year-old woman was admitted to the hospital four times from November 2007 to June 2009. In this complex case, the patient had silicosis complicated by broncholithiasis, oesophagobronchial fistulas, and relapsed tuberculosis. She had worked as a stone crusher for 3 years and was exposed to a large amount of quartz dust. Barium oesophagography, gastroesophageal endoscopy, and biopsy suggested oesophageal-related chronic inflammation and ulceration, which may have caused the repeated oesophagobronchial fistulas. Bronchoscopy revealed a free broncholithiasis in the left mainstem bronchus. The patient was admitted a fourth time because of silicotuberculosis relapse. After 9 months of antituberculosis treatment, the patient recovered and was still clinically well at the time of this writing.

Silicotuberculosis with Esophagobronchial Fistula and Broncholithiasis

A 69-year-old woman was admitted to hospital 4 times from November 2007 to June 2009. The patient had silicosis complicated by broncholithiasis, esophagobronchial fistula, and relapsed tuberculosis. She had worked as a stone crusher for 3 years and was exposed to a large amount of quartz dust. Barium esophagography, gastroesophageal endoscopy, and biopsy suggested esophageal-related chronic inflammation and ulcer, which probably caused the repeated esophagobronchial fistulas observed. Bronchoscopy revealed a free broncholithiasis in the left main bronchus. The patient was readmitted a fourth time, for the relapse of silicotuberculosis. After 9 months of antituberculous therapy, she was doing well until the recent last follow-up visit.

Occupational exposure to crystalline silica and gastric cancer: a systematic review and meta-analysis

Crystalline silica is a widely used industrial material that is readily available worldwide, and is one of the most common types of particulate mineral pollutants. It has been classified as a group 1 human carcinogen of the respiratory system; however, whether it is linked to gastric cancer remains uncertain. We conducted a systemic review and meta-analyses to search for evidence of the relationship between gastric cancer and occupational exposure to crystalline silica. We searched for articles on occupations involving silica exposure and gastric cancer studies up to December 2014. Pooled-risk estimates of the association between occupational crystalline silica exposure and risk of gastric cancer were calculated by a random effects model. Metaregression analyses of industry type and histological confirmation status, study design and industrial subgroup analyses were performed. 29 articles, including 9 case-control and 20 cohort studies, were analysed. The overall summary effects size was 1.25 (95% CI 1.18 to 1.34) for the association of occupational silica exposure with gastric cancer. Both heterogeneity and publication bias were partially attenuated after subgroup analyses. Heterogeneity of studies was attenuated after metaregression by industry. Higher overall effects were observed in the mining and foundry industries. We found a significant relationship between occupational crystalline silica exposure and gastric cancer. Our results were strengthened by various subgroup analyses and, considering the biological plausibility of our premise, further studies are required to better understand this association.

Occupational risks of esophageal cancer in Taiwanese men

This study aims to explore whether certain occupations were associated with the risk of esophageal squamous cell carcinoma (ESCC) in Taiwan. In a hospital-based case-control study, we collected 326 newly diagnosed ESCC patients and 386 age-matched controls (the ratio of case patients: controls = 1:1-2). All respondents completed a questionnaire, including 33 occupations in which environments potential exposure to cancer-related hazards are present. Workers with dust and metal exposure were categorized into Groups A and B, respectively. Relative risks for ESCC were estimated by odds ratios adjusting for covariates (AOR). Compared with the controls, farmer/gardener (AOR = 2.08, 95% CI = 1.02-4.24) and workers in Group A (AOR = 2.80, 95% CI = 1.21-6.47) had significantly higher risk for developing ESCC. A tendency of increased risk was also found in workers in group B (OR = 5.72 95% CI = 2.33-14.03), but such association was not significant after adjusting for other covariates (AOR = 1.57, 95% CI = 0.54-6.61). Our results suggested that farmer/gardener and workers with exposure to dust had a significant excess risk of ESCC. This study added further evidence to the current knowledge that occupational hazards are important in the development of ESCC.

The changing face of esophageal cancer

The two main histological esophageal cancer types, adenocarcinoma and squamous cell carcinoma, differ in incidence, geographic distribution, ethnic pattern and etiology. This article focuses on epidemiology with particular reference to geographic and temporal variations in incidence, along with a review of the evidence supporting environmental and genetic factors involved in esophageal carcinogenesis. Squamous cell carcinoma of the esophagus remains predominantly a disease of the developing world. In contrast, esophageal adenocarcinoma is mainly a disease of western developed societies, associated with obesity and gastro-esophageal reflux disease. There has been a dramatic increase in the incidence of adenocarcinoma in developed countries in parallel with migration of both esophageal and gastric adenocarcinomas towards the gastro-esophageal junction.

Oesophageal cancer in Golestan Province, a high-incidence area in northern Iran - a review

Golestan Province, located in the south-east littoral of the Caspian Sea in northern Iran, has one of the highest rates of oesophageal cancer (OC) in the world. We review the epidemiologic studies that have investigated the epidemiologic patterns and causes of OC in this area and provide some suggestions for further studies. Oesophageal squamous cell carcinoma (OSCC) constitutes over 90% of all OC cases in Golestan. In retrospective studies, cigarettes and hookah smoking, nass use (a chewing tobacco product), opium consumption, hot tea drinking, poor oral health, low intake of fresh fruit and vegetables, and low socioeconomic status have been associated with higher risk of OSCC in Golestan. However, the association of tobacco with OSCC in this area is not as strong as that seen in Western countries. Alcohol is consumed by a very small percentage of the population and is not a risk factor for OSCC in this area. Other factors, such as polycyclic aromatic hydrocarbons, N-nitroso compounds, drinking water contaminants, infections, food contamination with mycotoxins, and genetic factors merit further investigation as risk factors for OSCC in Golestan. An ongoing cohort study in this area is an important resource for studying some of these factors and also for confirming the previously found associations.

Role of silis in esophageal cancer

Association of silica with diseases like cancers has been determined previously. This study was designed to determine the quantity of silis in flour produced in Golestan Province, and its relation to esophageal cancer (EC). We took flour samples from all flour millings in Golestan Province. Base-melting method in nickel cruise was used at 550°C. The extract was reduced with acids. Different silis concentrations in various regions were compared. P < 0.05 was considered statistically significant. The median silis concentration was 0.0030 g, the mean silis concentration was 0.008760 ± 0.004265 g in each 100 g flour. The difference of mean silis concentrations in various regions was not significant. No high level of silica was found in the flour of Golestan Province. We could not find any significant difference in various areas between silica contaminations. Studies on the consumed bread and rice in various regions of Golestan Province can be helpful.

Silica and oesophageal cancer

The growth of animal cells in culture can be stimulated very powerfully when they are allowed to extend upon a solid surface. In normal fibroblasts, the maximum is reached either on a plane surface with an area of 2500 micron 2 or on a narrow fibre with a length of 250 micron. This growth-stimulating effect of fibres could help to explain how asbestos causes cancer. All asbestiform minerals are complex mixtures of different lengths, but siliceous macrohairs with a uniform length are borne by several species of the grass genus Phalaris. Some of these species are common contaminants of the bread eaten in a part of Iran where oesophageal cancer has an unexplained high incidence. A pure preparation of 200 micron silica fibres from one of these species is a powerful promoter of cancer in the skin of mice. Similar fibres from millet (Seteria italica) are associated with the same disease in China, and plant silica has long been known to be associated the it in South Africa. In addition, a rare thoracic tumour, which normally only occurs after exposure to asbestos, has been detected among sugarcane farmers in the United States and in India; fine silica fibres are liberated into the air during the harvest.

Further evidence for a link between silica dust and esophageal cancer

Our objective was to examine the relationship between silicosis and esophageal cancer in Hong Kong. The mortality of esophageal cancer was investigated among caisson and non-caisson workers in a cohort of 2,789 male silicotic workers in Hong Kong during the period 1981-99. The standardized mortality ratio (SMR) was calculated using the Hong Kong general population rates as reference. The indirect method proposed by Axelson was used to adjust for the confounding effects of cigarette smoking and alcohol drinking. The SMR of esophageal cancer in the entire cohort was 2.22 (95% CI 1.36-3.43, based on 20 deaths) and was 4.21 (95% CI 1.81-8.30, based on 8 deaths) in the subgroup of caisson workers who had a higher exposure to silica dust. The relative risk of esophageal cancer for caisson silicotics was reduced to 2.34 after adjusting for the effects of smoking and alcohol drinking. No more excess risk of esophageal cancer was observed among non-caisson silicotic workers after the adjustments. This historical cohort study revealed that there was an increased mortality risk of esophageal cancer among silicotics who had worked in underground caissons in Hong Kong after adjusting for cigarette smoking and alcohol drinking. We believe that the excess risk of esophageal cancer mortality among caisson workers with silicosis could best be explained by the very heavy exposure to free silica dust in their working environment.

Sugarcane farming, occupational solvent exposures, and the risk of oral cancer in Puerto Rico

The work history information from a population-based case-control study conducted in Puerto Rico was analyzed using a job exposure matrix to investigate the relationship between occupational exposures and cancers of the oral cavity or pharynx. After adjustment for age, alcohol, smoking, and residence in a logistic model, the risk for cancer of the oral cavity, but not the pharynx, was significantly elevated among farm workers in the sugarcane industry (OR = 4.4, 95% CI = 1.4-13.6). An exposure-response trend was seen for cumulative exposure to solvents, with an OR = 3.2 (95% CI = 0.8-12.6) in the highest exposure category. The overall contribution to the risk of cancer of the oral cavity or pharynx associated with occupational exposures in Puerto Rico appears to be small, however, the elevated risks were seen among sugarcane farmers and subjects with high cumulative exposure to solvents.

Nested case-control study of esophageal cancer in relation to occupational exposure to silica and other dusts

BACKGROUND

Standardized proportionate mortality ratio (SPMR) was found to be 2.2 (95% CI = 1.3-3.5) for esophageal cancer (EC) among workers exposed to refractory brick dust in a large iron-steel complex in China.

METHODS

A nested case-control design within a cohort of industrial workers. One hundred and twenty-five EC cases and 250 controls were identified from the death registry file. Interviews were conducted of the next of kin for past exposure information on job, domestic, and lifestyle factors. History of occupational exposure to various dusts was reconstructed from personnel files and by interviewing colleagues utilizing a job-exposure matrix.

RESULTS

After adjusting for confounders, occupational exposure to silica dust was the most important risk factor among all variables investigated, with a 2.8-fold risk and a clear dose-response by length of exposure. Alcohol drinking (OR = 1.8) and coal cooking (OR = 2.0) were risk factors and high consumption of fruit diet (OR = 0.5) and meat diet (OR = 0.6) were protective factors.

CONCLUSIONS

The relationship between occupational exposure to silica dust and the risk of EC found in an earlier SPMR study was confirmed. Ingestion of silica particles after lung clearance may increase the risk of EC among workers exposed to silica.

Some recent advances in studies of silicon in higher plants

In comparison with elements commonly associated with the nutrition of higher plants, silicon has received relatively little attention. Recently developed techniques have, however, demonstrated its occurrence in a wide range of tissues and species. Grasses are heavy accumulators, but considerable variation occurs between and within species. The factors involved in uptake, translocation and deposition in different species are not fully understood. Deposition has been investigated in the roots of a number of species. Active or passive uptake or almost complete exclusion has been observed. While deposits most frequently occur in cell wall layers or in cell lumina of the root endodermis, the major influx remains in a soluble form and is translocated to the shoot. Deposition is heavy in grass and cereal inflorescence bracts. Silica has also been detected in the epicarp hairs of cereal grains, and evidence is presented regarding the time course of its accumulation in these hairs. It is suggested that such deposition cannot be entirely attributed to a passive transpiration mediated mechanism. The significance of these deposits is discussed in relation to plant growth and development, and to wider aspects associated with human health.

Retrospective cohort study of risk-factors for esophageal cancer in Linxian, People's Republic of China

A retrospective cohort study of esophageal (including gastric cardia) cancer was conducted to examine dietary and other potential risk factors in Linxian, a high-risk area in P.R. China. Study subjects were identified based on participation in a cytology examination conducted in 1974. They were interviewed in 1989 to obtain information on esophageal cancer risk-factors and identify new cases and deaths. A total of 1,162 subjects from the analytic cohort of 12,693 were determined to have developed esophageal cancer over the 15-year follow-up period. Results indicate that increased age, male gender, a positive family history, low education level, surface-water use, and pork consumption were the strongest risk factors for esophageal cancer identified in this cohort, while use of corn as a primary staple and infrequent consumption of fresh vegetables also were possible risk factors. Traditional or suspected risk factors for esophageal cancer in this and other populations--smoking and alcohol use, and pickled vegetable and moldy food consumption--were not risk factors in this study. Some variation in risk was seen based on the subject's cytology result from 1974. We conclude that dietary factors appear to play a role in the etiology of esophageal cancer in this high-risk population, but are less important than other constitutional factors such as age, gender, and family history.

Cancer prevention trials in China and Finland

Intervention studies are now viewed as a useful and necessary approach to understanding the relation between nutrition and cancer. Over 20 such studies have been initiated in the past 7 years. Foreign countries may be an attractive site for such investigations, mainly because of desirable population characteristics such as unusually high rates of the cancer being studied, low dietary intake of potential chemopreventive nutrients, stability of the population, and high compliance, and also because of favorable logistical aspects including existing medical, social, or governmental structures that facilitate delivery of the intervention, ongoing cancer registries for endpoint determination, and reduced cost. The three basic elements of an intervention trial, identification and recruitment of a study population, delivery of the intervention and assessment of compliance, and ascertainment of endpoints, are the same in a foreign country as in the United States, but there are a number of special considerations, most notably communication difficulties due to language differences and distance between collaborators, which complicate foreign trials both before and during implementation. The basic elements and status of ongoing trials in China and Finland are presented.

Water contamination and esophageal cancer at Gassim Region, Saudi Arabia

Between January 1980 and December 1982, 183 patients with histologically confirmed carcinoma of the esophagus who were referred to a tertiary referral hospital were studied. Thirty-two (17%) patients were referred from Gassim Region at the north central part of Saudi Arabia. In contrast, only 5% of total cancer patient referrals were from this area. A case-control study showed a significant regional difference within Saudi Arabia and the most referrals from Gassim area. A prospective case-control study showed persistently high numbers of referrals from that region during 1983-1987. When patients from Gassim Region were compared with those referred from other locations, no statistical differences were noted between the two groups except for the source of drinking water. Water analysis from Gassim area showed a high solid content with elevated levels of calcium, magnesium, and to a lesser extent, chromium iron, cadmium, and cobalt. Traces of petroleum oil were found in five of six water samples from Gassim during 1983, compared with 3 of 49 samples from other areas. Mutagenicity tests on water specimens form Gassim Region indicated the presence of possible carcinogens. It is being suggested that the high prevalence of esophageal cancer in this region may be related to contamination of water by impurities such as petroleum oils. Malnutrition, particularly vitamin A deficiency, as well as other factors may have promoted such malignancies.

Correlations of dietary intake and blood nutrient levels with esophageal cancer mortality in China

Using dietary, blood nutrient, and esophageal cancer mortality data from 65 Chinese counties, we examined several correlations to help provide clues to the influence of diet and nutrition on the geographic variation of esophageal cancer in China. Esophageal cancer mortality was significantly inversely related to reported fruit consumption and to plasma ascorbic acid concentration. The age-adjusted mortality rates were more than three times higher for counties in the lowest compared with the highest quartile of fruit intake or plasma vitamin C. Positive correlations with intake of moldy vegetables were observed but not with tobacco and alcohol consumption. There were suggestive inverse associations with blood selenium and riboflavin but little effect of fat-soluble vitamins. Limitations of ecological data preclude causal inferences, but the relationships provide leads to dietary factors that may contribute to the exceptionally high rates of esophageal cancer in several areas of China.

A case-control study of cancer of the esophagus and gastric cardia in Linxian

A case-control study involving interviews with 1,244 patients (758 males and 486 females) with cancer of the esophagus or gastric cardia and 1,314 population-based controls (789 males, 525 females) was carried out in Linxian, a rural county in North Central China with one of the world's highest mortality rates for these tumors. Cancer risks tended to rise with increasing intake of wheat and corn, but no association was found with adult intake of pickled vegetables, the leading a priori suspect, and risks were not elevated among those consuming low quantities of fresh vegetables or fruits. Few differences in preparation or storage of food or water were detected, although cancer patients reported less fluid intake than controls. Few persons reported drinking alcoholic beverages. Smoking was reported by 61% of the male cases and was a mild risk factor, related more to cancer of the cardia than of the esophagus. The risk was increased by 70% among those whose parents had esophageal or stomach cancer, but only slightly among those whose spouses had such cancers, suggesting that exposure early in life and/or genetic effects may be involved.

Epidemiology of cancer of the esophagus in Canada: 1931-1984

Canadian patterns of morbidity and mortality from malignancies of the esophagus for the periods 1970-1980 and 1931-1984, respectively, were examined. Age-standardized morbidity and mortality rates have increased significantly for men during the two periods studied (p less than 0.01). Analysis of age-specific rates indicates that increases in age-standardized mortality rates for men are mostly attributable to significant increases in age-specific rates for five of the eight age groups studied. In contrast, age-standardized mortality rates for women have declined significantly during the same period (p less than 0.001), with significant declines in age-specific mortality rates noted for four of the eight age groups studied. Age-standardized morbidity rates for men have changed significantly for two age groups (p less than 0.05), with the rate of change of a third group being of borderline significance (p less than 0.10). Age-standardized morbidity rates for women have not changed significantly during the period 1970-1980 (p = 0.97), which was also characteristic of each of the eight age-specific morbidity rates studied (p greater than 0.40).

Biogenic silica fibre promotes carcinogenesis in mouse skin

Silica fibres derived from plants are common contaminants of human diet in certain regions of the world where oesophageal cancer reaches extremely high incidences. We show here that one of these types of fibre (derived from Phalaris canariensis L) promotes the occurrence of tumours in the skin of mice initiated with a polycyclic carcinogen. Three experiments are described. In the first, the grain which bears these fibres was added to the diet. This did not result in any abnormality in any part of the gastrointestinal tract, but there was a significant induction of tumours in the skin around the mouth and nose; these were the areas of the body surface which most frequently came into contact with the grain. In the second experiment, the mice were separated from the grain by an intervening wire gauze barrier; a similar number of tumours appeared on initiated mice treated in this way. In this case, contact now occurred most frequently on the dorsal surface, which was rubbed against the gauze barrier, and it was on this surface that the tumours appeared. No tumours appeared if the grain was removed. In the third experiment, pure fibres were isolated from the surface of the grain and boiled in strong nitric acid so as to remove any organic material. When these acid-cleaned fibres were applied to the initiated skin with light pressure, they promoted carcinogenesis in the same way as croton oil. In each experiment the majority of tumours produced were benign neoplasms, together with at least one squamous carcinoma. It seems possible that the size and shape of these fibres are the critical properties determining their promoting activity. Their mean diameter is 15 microns, their modal length close to 200 microns, and they are sharply pointed with a tip diameter of 0.5 micron.

Pesticides and breast cancer, popcorn and colorectal cancer: innovation versus fashion in dietary epidemiology

Organochlorine insecticides and polychlorinated biphenyls (PCBs) have been found to be carcinogenic in animal studies. Eight of these insecticides and PCBs have been detected in human milk samples. Their possible contribution to breast cancer has never been seriously studied. Substances which cause scarring or provide anchorage when embedded in tissue can contribute to carcinogenesis. Sharp outer fragments of popcorn kernels may contribute to the type of tissue fibrosis associated with colorectal cancer. Lack of innovation in dietary cancer epidemiology is discussed.