Cancer risks in populations living near landfill sites in Great Britain

Multifaceted perspectives of detecting and targeting solid tumors

Solid tumors are the most prevalent form of cancer. Considerable technological and medical advancements had been achieved for the diagnosis of the disease. However, detection of the disease in an early stage is of utmost importance, still far from reality. On the contrary, the treatment and therapeutic area to combat solid tumors are still in its infancy. Conventional treatments like chemotherapy and radiation therapy pose challenges due to their indiscriminate impact on healthy and cancerous cells. Contextually, efficient drug targeting is a pivotal approach in solid tumor treatment. This involves the precise delivery of drugs to cancer cells while minimizing harm to healthy cells. Targeted drugs exhibit superior efficacy in eradicating cancer cells while impeding tumor growth and mitigate side effects by optimizing absorption which further diminishes the risk of resistance. Furthermore, tailoring targeted therapies to a patient's tumor-specific molecular profile augments treatment efficacy and reduces the likelihood of relapse. This chapter discuss about the distinctive characteristics of solid tumors, the possibility of early detection of the disease and potential therapeutic angle beyond the conventional approaches. Additionally, the chapter delves into a hitherto unknown attribute of magnetic field effect to target cancer cells which exploit the relatively less susceptibility of normal cells compared to cancer cells to magnetic fields, suggesting a future potential of magnetic nanoparticles for selective cancer cell destruction. Lastly, bioinformatics tools and other unconventional methodologies such as AI-assisted codon bias analysis have a crucial role in comprehending tumor biology, aiding in the identification of futuristic targeted therapies.

Self-reported symptoms of ocular allergy and its comorbid factors among residents living near a landfill site in Ghana

Residents close to landfill sites may be exposed to long-term emitted toxic compounds that may have effects on their eyes. The aim of this study was to determine the prevalence of symptomatic ocular allergy and its comorbid factors among residents living near a landfill site in Ghana. An exploratory cross-sectional design involving 400 inhabitants living around a landfill site was employed. The prevalence of symptomatic ocular allergy was 59.3%. In a bivariate analysis, comorbid conditions including respiratory disease, coughing, flu, cholera, skin disease, diarrhoea, and hypertension predicted symptomatic ocular allergy. However, only cholera remained a significant predictor of symptomatic ocular allergy in the multivariate analysis. Symptomatic ocular allergy was high among inhabitants around the landfill site in Ghana. While proper design and management of landfills in Ghana is crucial, further longitudinal and clinical studies are required to clinically establish the link between landfill and ocular allergy.

Distribution characteristics and potential ecological risk assessment of heavy metals in soils around Shannan landfill site, Tibet

At present, sanitary landfill is mainly used for domestic waste treatment in Shannan City, Tibet. However, there are few studies on heavy metals in the soil around the landfill in Shannan city. Therefore, the surrounding soil of Luqionggang landfill in Shannan City, Tibet Autonomous Region, is taken as the research object. In the study, the geo-accumulation index method, Nemerow comprehensive pollution index method and potential ecological risk index method are mainly used to evaluate the pollution and risk of heavy metals in the soil around the landfill site. The main results are as follows: The average pH value of the soil around the landfill site is 9.37, belonging to the strong alkaline range. The average values of heavy metals Hg and Ni in soil exceeded the background content, and the average contents of other heavy metals Cu, Pb, Zn, Cr, As and Cd did not exceed the background content. The average content of these eight heavy metals did not exceed the screening value of the national soil environmental quality standard. In the horizontal direction, the average content of heavy metal elements Cu, Cr, Cd, Hg and Ni is relatively high in the west. The average content of heavy metals As, Zn and Pb in the north, east and south is slightly higher than that in the west. And the farther away from the landfill, the less the soil is affected by heavy metals. The evaluation results of geo-accumulation index show that heavy metal Hg is the most affected. The average value of the comprehensive pollution index is 2.969, which is between 2 and 3, belonging to the moderate pollution level. And the west side of the landfill (downstream area) is greatly affected. The evaluation results of potential ecological hazard pollution index show that the potential risk index of single pollutants of heavy metals Cu, Pb, Zn, Cr, Ni, As and Cd belongs to low ecological hazard level, and the potential risk index of single pollutants of heavy metal Hg belongs to relatively heavy ecological hazard level. On the whole, the total potential risk coefficient belongs to medium pollution hazard degree. According to the correlation analysis, there is no significant correlation between heavy metal elements As and Hg and the other six heavy metal elements. In addition, the pollution source of heavy metal As may be mainly soil forming factors and the pollution source of Hg may be mainly human factors.

Household solid waste management practices and perceptions among residents in the East Coast of Malaysia

BACKGROUND

Poor waste disposal practices hamper the progress towards an integrated solid waste management in households. Knowledge of current practices and perception of household solid waste management is necessary for accurate decision making in the move towards a more sustainable approach. This study investigates the household waste practices and perceptions about waste management in Panji, one of the sub-districts in Kota Bharu, Kelantan, Malaysia.

METHODS

A stratified random sampling technique using a cross-sectional survey questionnaire was used to collect data. A total of 338 households were interviewed in the survey and data were analyzed using SPSS. Chi-square goodness of fit test was used to determine the relationships between categorical variables, whereas Chi-square bivariate correlation test was performed to observe the correlation between the perceptions of waste segregation with socio-demographic background of the respondents. The correlation between perception of respondents with the locality, house type and waste type were also conducted. Principal component analysis was used to identify grouping of variables and to establish which factors were interrelated in any given construct.

RESULTS

The results of the study revealed that 74.3 % of households disposed of food debris as waste and 18.3% disposed of plastic materials as waste. The study also showed that 50.3% of the households segregate their waste while 49.7% did not. About 95.9% of the respondents were aware that improper waste management leads to disease; such as diarrhea and malaria. There were associations between locality, age and house type with waste segregation practices among respondents (Chi-square test, p<0.05). Associations were also found between locality with the perception of improper waste management which lead to disease (Chi-square test, p<0.05). Principal Component Analysis showed that 17.94% of the variance has high positive loading (positive relationship) with age, marital status and, type of house.

CONCLUSION

This study highlights the importance to design waste separation programs that suit the needs of targeted population as a boost towards sustainable solid waste management practices.

Wild black rats (Rattus rattus Linnaeus, 1758) as zoomonitor of genotoxicity and systemic toxicity induced by hazardous emissions from Abule Egba unsanitary landfill, Lagos, Nigeria

Wild black rats (Rattus rattus) inhabiting Abule Egba landfill (AEL) were used as zoomonitor to assess health risk associated with exposure to hazardous chemicals from landfills. Twenty five R. rattus (16♂ and 9♀) captured within AEL and 15 (9♂ and 6♀) (control) caught from Iyano Ipaja (10 km away from AEL) were examined for bone marrow micronucleated polychromatic erythrocytes (MNPCE) and polychromatic erythrocytes/normochromatic erythrocytes (PCE/NCE) ratio, abnormal sperm morphology, alterations in hematological indices and erythrocyte morphology, and histopathology of the viscera using standard protocols. There was significant (p < 0.05) increase in MNPCE but decrease PCE/NCE ratio in bone marrow cells of exposed rats than the reference site. MNPCE was insignificantly higher in male than females. Cauda epididymal sperms from exposed rats showed significant high frequency of teratozoospermia. Erythrocyte count, hemoglobin concentrations, percentage hematocrits, mean corpuscular hemoglobin concentrations, leucocyte count, and lymphocytes decreased while mean corpuscular volume, neutrophils, and mean corpuscular hemoglobin increased in the exposed rats compared to the control. Also, abnormal erythrocyte morphology: acanthocytes, codocytes (target cells), schizocytes, and tear drops significantly increased in the exposed rats. Marginal sexual dimorphism was observed between males and females in the incidence of hematological indices. Histopathological lesions including interstitial edema, hemorrhage, lymphoid depletion, cellular infiltrations, proliferation of the alveolar pneumocytes, necrosis, tissue degeneration, and reduced germinal epithelium were observed in the testes, liver, lungs, heart, kidney, and spleen from the exposed rats compared to the control. Some physicochemicals and metals analyzed in leachates from the landfill are capable of inducing genome instability and systemic toxicity in the exposed rats. Rattus rattus exposed to hazardous chemicals from AEL harbored somatic and germ cell mutations, and tissue damage compared to the control rats. We suggest that R. rattus are useful sentinel for genotoxicity and system toxicity assessment of landfill-polluted sites.Graphical abstract.

Renal impairment assessment on adults living nearby a landfill: Early kidney dysfunction biomarkers linked to the environmental exposure to heavy metals

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Health risk of the neighboring population of the Mbeubeuss landfill (Senegal).

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Assessment of the impact of Cd/Pb exposure through dysfunction renal biomarkers.

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Specific increases of a set of early dysfunction renal biomarkers in exposed subjects.

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Glomerular and tubular dysfunction in exposed subjects.

The aim of this study was to assess the integrity and kidney overall functional capacity of subjects exposed to landfill emissions. Urine and blood levels of Pb and Cd, and several of the newly biomarkers of nephrotoxicity (Kim Injury Molecule 1 (KIM-1), alpha-1 Microglobulin (α1 M), beta-2 Microglobulin (β2 M), Cystatin-C (Cyst C), Clusterin, alpha-glutathione S-transferase (GSTα), pi-glutathione S-transferase (GSTπ), Tissue Inhibitor of Metalloproteinase-1 (TIMP1), Calbindin, Neutrophil Gelatinase-Associated Lipocalin (NGAL), Osteopontin (OPN), (Retinol Binding Protein(RBP), Liver-type Fatty Acid-Binding Protein (FABP-1), Trefoil Factor 3 (TFF3), Collagen VI) were measured in order to assess glomerular and tubule damage in adults living near a landfill.

Our results indicate glomerular dysfunction in exposed subjects, and supported evidence of necrosis of proximal and distal tubule epithelial cells as specific biomarkers began to appear in the urine.

Positive correlation by Pearson test were obtained between : blood Pb and B-OPN, B-Cyst C, Calbindin, U-KIM-1, TIMP1, U-OPN, and U-Clusterin; and also, between urinary Cd and TIMP1, B-Clusterin, U-OPN, FABP-1, Albumin, and U-Clusterin. The relation between biomarkers of Cd/Pb exposure and early effect biomarkers in this study clearly predicts the future risk of severe kidney injury in subjects living close to the landfill.

A Geographic Information System-Based Indicator of Waste Risk to Investigate the Health Impact of Landfills and Uncontrolled Dumping Sites

Uncontrolled and poor waste management practices are widespread. The global health impact of hazardous waste exposure is controversial, but the excess of some diseases appears to be consistent. The Geographic Information System (GIS, ESRI Inc., Rome, Italy) method used to estimate the waste risk exposure, in an area with many illegal waste dumps and burning sites, is described. A GIS geodatabase (ESRI ArcGIS format) of waste sites’ data was built. A municipal GIS-based indicator of waste risk (Municipal Risk Index: MRI) has been computed, based on type and quantity of waste, typology of waste disposal, known or potential environmental contamination by waste and population living near waste sites. 2767 waste sites were present in an area 426 km² large. 38% of the population lived near one or more waste sites (100 m). Illegal/uncontrolled waste dumps, including waste burning areas, constituted about 90% of all sites. The 38 investigated municipalities were categorized into 4 classes of MRI. The GIS approach identified a widespread impact of waste sites and the municipalities likely to be most exposed. The highest score of the MRI included the municipalities with the most illegal hazardous waste dumps and burning sites. The GIS-geodatabase provided information to contrast and to prosecute illegal waste trafficking and mismanagements.

Assessment of the environmental impact of sanitary and unsanitary parts of a municipal solid waste landfill

Only seven regional MSWLF in Serbia are considered sanitary, while about 3500 landfills operate without proper pollution control. This paper presents a unique opportunity to evaluate the impact of a closed landfill, and a new sanitary landfill, which are located next to each other. The following methodologies for the landfill impact assessment were applied, based on data from 2012 to 2017: Landfill water pollution index (LWPI) and Nemerow index (PI_GW) for groundwater, and the geo-accumulation (I_geo) and ecological risk (ERⁱ) indices and several PAH ratios for soil. The performance of the leachate control system was evaluated using two adapted pollution indices: LPI and the Nemerow index (PI_L). According to the obtained LWPI and PI_GW values, the quality of groundwater at the new landfill is improving (LWPI = 1.05-2.62; PI_GW = 0.52-1.29), while no significant changes were observed for the old landfill (LWPI = 3.06-5.13; PI_GW = 2.03-4.78). High concentrations of ammonia nitrogen (1.01-22.74 mg/l), Fe (0.76-57.11 mg/l), Ni (5.80-230.09 μg/l), Pb (4.2-202.4 μg/l) and ∑PAH₁₆ (150.93-189.55 ng/l) show the strong influence of the landfill on the groundwater quality at the old landfill, indicating the need for additional remediation action. High concentrations of Ni (21.9-133.0 mg/kg) and Cr (8.5-277.0 mg/kg) in the analyzed soil compared to other studies, as well as moderate I_geo values (I_geoNi = 0.36-1.88; I_geoCr = -1.20-1.52), raise concern and suggest the need for further monitoring. The high ERⁱ (158.6-295.0) and I_geo values (0.91-2.30) of Hg show significant potential ecological risk. LPI and PI_L values for early methanogenic phase leachate demonstrates the need to improve the leachate treatment system. The monitoring data and applied pollution indices indicate that Cr and As should be added to the EU Watch List of emerging substances, at least regarding EU potential candidate countries.

Community Health Survey of Residents Living Near a Solid Waste Open Dumpsite in Sabak, Kelantan, Malaysia

The management of waste materials is a serious problem worldwide, especially in urbanizing countries like Malaysia. This study was conducted to compare the prevalence of health symptoms and diseases diagnosed among residents exposed to the solid waste open dumpsite in the suburb of Sabak with the non-exposed community. Research related to exposure to solid waste dumping with complete health problems has never been combined in one study. A comparative cross-sectional study was conducted. The exposed group included residents within a 1 km radius and the non-exposed group included residents between a 2.5 and 4.0 km radius from the dumpsite. The selected residents were interviewed using validated, structured questionnaires. A total of 170 residents from the exposed group and 119 residents from the non-exposed group were selected. The mean (SD) duration time of residence was 22.6 (18.9) years for the exposed group and 15.0 (12.0) years for the non-exposed group. Dumpsite exposure was significantly associated with sore throat (adjusted odd ratio (AOR) 1.88; 95% confidence interval (CI): 1.05, 3.38; p = 0.031), diabetes mellitus (AOR 2.84; 95% CI: 1.10, 7.30; p = 0.021) and hypertension (AOR 2.56; 95% CI: 1.27, 5.13; p = 0.006). This study provides evidence that the unsanitary solid waste disposal in Malaysia is hazardous to the health of residents in the surrounding 1 km, and efforts are needed to minimize the hazards.

The effects of particle-induced oxidative damage from exposure to airborne fine particulate matter components in the vicinity of landfill sites on Hong Kong

The physical, chemical and bioreactivity characteristics of fine particulate matter (PM_2.5) collected near (<1 km) two landfill sites and downwind urban sites were investigated. The PM_2.5 concentrations were significantly higher in winter than summer. Diurnal variations of PM_2.5 were recorded at both landfill sites. Soot aggregate particles were identified near the landfill sites, which indicated that combustion pollution due to landfill activities was a significant source. High correlation coefficients (r) implied several inorganic elements and water-soluble inorganic ions (vanadium (V), copper (Cu), chloride (Cl^-), nitrate (NO₃^-), sodium (Na) and potassium (K)) were positively associated with wind flow from the landfill sites. Nevertheless, no significant correlations were also identified between these components against DNA damage. Significant associations were observed between DNA damage and some heavy metals such as cadmium (Cd) and lead (Pb), and total Polycyclic Aromatic Hydrocarbons (PAHs) during the summer. The insignificant associations of DNA damage under increased wind frequency from landfills suggested that the PM_2.5 loading from sources such as regional sources was possibly an important contributing factor for DNA damage. This outcome warrants the further development of effective and source-specific landfill management regulations for particulate matter production control to the city.

Health and Environmental Risks of Residents Living Close to a Landfill: A Case Study of Thohoyandou Landfill, Limpopo Province, South Africa

The by-products of solid waste deposited in a landfill has adverse effects on the surrounding environment and humans living closer to landfill sites. This study sought to test the hypothesis that the deposition of waste on landfill has an impact on the surrounding environment and residents living closer to it. This was achieved by evaluating the perception of the respondents drawn from people living close (100-500 m) and far (1-2 km) from the landfill site, concerning environmental issues, health problems, and life satisfaction. Results from the study showed that 78% of participants living closer to the landfill site indicated serious contamination of air quality evident from bad odours linked to the landfill site. Illnesses such as flu, eye irritation and weakness of the body were frequently reported by participants living closer to the landfill than those living far from the landfill. More than half of the participants (56%) living closer to the landfill indicated fear of their health in the future. Thus, the participants living closer to the landfill site were less satisfied with the location of their community with respect to the landfill, than those living far from the landfill site. Therefore, the need for a landfill gas (LFG) utilisation system, proper daily covering of waste and odour diluting agents are necessary to reduce the problems of the residents living closer to the landfill site.

Preremedial assessment of the municipal landfill pollution impact on soil and shallow groundwater in Subotica, Serbia

Most regional municipal solid waste landfills in Serbia are operated without control of landfill leachate and gas or with no regard for implementation of national and European legislation. For the first time in Serbia, groundwater and soil at a landfill were subject to systematic annual monitoring according to national, European legislation and adopted methodologies. Characterisation of the groundwater and soil samples from the landfill included ten metals (Fe, Mn, As, Zn, Cd, Pb, Ni, Cr, Cu and Hg), 16 EPA PAHs, nutrients and certain physicochemical parameters, in order to assess the risks such poorly controlled landfills pose to the environment. This impact assessment was performed using specially adapted pollution indices: LWPI, the Single factor pollution index and the Nemerow index for groundwater, and geo-accumulation index, ecological risk factor and selected rations of PAHs for soil. The data analysis included multivariate statistical methods (factor analysis of principal component analysis (PCA/FA)) in order to assess the extent of the contaminants detected in the groundwater and soil samples. The pollution indices (LWPI: 3.56-8.89; Nemerow index: 2.02-3.78) indicate the quality of the groundwater at the landfill is degrading over time, with PAH₁₆, TOC, Cr, Cu, Pb and Zn as the substances of greatest concern. Heavy metals Hg (I_geo≤3.14), Pb (I_geo≤2.22), Cr (I_geo≤3.31) and Cu (I_geo≤2.16) represent the worst soil contamination. Hg has moderate (52.9) to very high (530.0) potential ecological risk, demonstrating the long-term potential effects of bioaccumulation and biomagnification. The results of this work indicate that Cr and Cu should possibly be added to the EU Watch List of emerging substances. This proposition is substantiated by relevant state and alike environmental information from nations in the region. This study demonstrates the need to develop a model for prioritization of landfill closure and remediation based on environmental risk assessment.

Micronuclei and other nuclear anomalies in exfoliated buccal cells of urban solid waste collectors and recyclers in southern Brazil

Workers involved in urban solid waste collection may be exposed to various environmental contaminants, including chemical pollutants, which might be mutagenic and increase the risk of diseases such as cancer. Evaluation of DNA damage in workers in this field are still scarce. This study aims to evaluate mutagenic and cytotoxic effects in workers involved in the collection and segregation of urban solid waste generated in southern Brazil. Municipal solid waste collectors were recruited in two municipalities of the state of Rio Grande do Sul. The control group was composed of workers of the education and commerce areas, with no exposure to known genotoxic agents. Slides of exfoliated buccal cells were analyzed to estimate the frequency of micronuclei (MN) as well as other nuclear abnormalities, such as broken-egg/bud, binucleation and karyorrhexis. The analyses of 44 workers and 45 control subjects have shown that the frequencies of MN, binucleated cells and karyorrhexis in the exposed workers were significantly higher than in the control group. In the exposed group, frequencies of MN and binucleated cells showed a significant positive correlation. The other cytogenetic parameters were not correlated among each other or with age and exposure time. These results indicate that the workers involved in urban solid waste collection are exposed to mutagenic and cytotoxic agents.

Hazardous waste and health impact: a systematic review of the scientific literature

Waste is part of the agenda of the European Environment and Health Process and included among the topics of the Sixth Ministerial Conference on Environment and Health. Disposal and management of hazardous waste are worldwide challenges. We performed a systematic review to evaluate the evidence of the health impact of hazardous waste exposure, applying transparent and a priori defined methods. The following five steps, based on pre-defined systematic criteria, were applied. 1. Specify the research question, in terms of "Population-Exposure-Comparators-Outcomes" (PECO).

POPULATION

people living near hazardous waste sites; Exposure: exposure to hazardous waste; Comparators: all comparators; Outcomes: all diseases/health disorders. 2. Carry out the literature search, in Medline and EMBASE. 3. Select studies for inclusion: original epidemiological studies, published between 1999 and 2015, on populations residentially exposed to hazardous waste. 4. Assess the quality of selected studies, taking into account study design, exposure and outcome assessment, confounding control. 5. Rate the confidence in the body of evidence for each outcome taking into account the reliability of each study, the strength of the association and concordance of results.Fifty-seven papers of epidemiological investigations on the health status of populations living near hazardous waste sites were selected for the evidence evaluation. The association between 95 health outcomes (diseases and disorders) and residential exposure to hazardous waste sites was evaluated. Health effects of residential hazardous waste exposure, previously partially unrecognized, were highlighted. Sufficient evidence was found of association between exposure to oil industry waste that releases high concentrations of hydrogen sulphide and acute symptoms. The evidence of causal relationship with hazardous waste was defined as limited for: liver, bladder, breast and testis cancers, non-Hodgkin lymphoma, asthma, congenital anomalies overall and anomalies of the neural tube, urogenital, connective and musculoskeletal systems, low birth weight and pre-term birth; evidence was defined as inadequate for the other health outcomes. The results, although not conclusive, provide indications that more effective public health policies on hazardous waste management are urgently needed. International, national and local authorities should oppose and eliminate poor, outdated and illegal practices of waste disposal, including illegal transboundary trade, and increase support regulation and its enforcement.

Risk factors for central nervous system tumors in children: New findings from a case-control study

Background

Central nervous system tumors (CNS) are the most frequent solid tumor in children. Causes of CNS tumors are mainly unknown and only 5% of the cases can be explained by genetic predisposition. We studied the effects of environmental exposure on the incidence of CNS tumors in children by subtype, according to exposure to industrial and/or urban environment, exposure to crops and according to socio-economic status of the child.

Methods

We carried out a population-based case-control study of CNS tumors in Spain, covering 714 incident cases collected from the Spanish Registry of Childhood Tumors (period 1996–2011) and 4284 controls, individually matched by year of birth, sex, and autonomous region of residence. We built a covariate to approximate the exposure to industrial and/or urban environment and a covariate for the exposure to crops (GCI) using the coordinates of the home addresses of the children. We used the 2001 Census to obtain information about socio-economic status (SES). We fitted logistic regression models to estimate odds ratios (ORs) and 95% confidence intervals (95%CIs).

Results

The results for all CNS tumors showed an excess risk (OR = 1.37; 95%CI = 1.09–1.73) for SES, i.e., children living in the least deprived areas had 37% more risk of CNS tumor than children living in the most deprived areas. For GCI, an increase of 10% in crop surface in the 1-km buffer around the residence implied an increase of 22% in the OR (OR = 1.22; 95%CI = 1.15–1.29). Children living in the intersection of industrial and urban areas could have a greater risk of CNS tumors than children who live outside these areas (OR = 1.20; 95%CI = 0.82–1.77). Living in urban areas (OR = 0.90; 95%CI = 0.65–1.24) or industrial areas (OR = 0.96; 95%CI = 0.81–1.77) did not seem to increase the risk for all CNS tumors together. By subtype, Astrocytomas, Intracranial and intraspinal embryonal tumors, and other gliomas showed similar results.

Conclusion

Our results suggest that higher socioeconomic status and exposure to crops could increase the risk of CNS tumors in children.

A systematic critical review of epidemiological studies on public health concerns of municipal solid waste handling

AIMS

The ultimate aim of this review was to summarise the epidemiological evidence on the association between municipal solid waste management operations and health risks to populations residing near landfills and incinerators, waste workers and recyclers. To accomplish this, the sub-aims of this review article were to (1) examine the health risks posed by municipal solid waste management activities, (2) determine the strengths and gaps of available literature on health risks from municipal waste management operations and (3) suggest possible research needs for future studies.

METHODS

The article reviewed epidemiological literature on public health concerns of municipal solid waste handling published in the period 1995-2014. The PubMed and MEDLINE computerised literature searches were employed to identify the relevant papers using the keywords solid waste, waste management, health risks, recycling, landfills and incinerators. Additionally, all references of potential papers were examined to determine more articles that met the inclusion criteria.

RESULTS

A total of 379 papers were identified, but after intensive screening only 72 met the inclusion criteria and were reviewed. Of these studies, 33 were on adverse health effects in communities living near waste dumpsites or incinerators, 24 on municipal solid waste workers and 15 on informal waste recyclers. Reviewed studies were unable to demonstrate a causal or non-causal relationship due to various limitations.

CONCLUSION

In light of the above findings, our review concludes that overall epidemiological evidence in reviewed articles is inadequate mainly due to methodological limitations and future research needs to develop tools capable of demonstrating causal or non-causal relationships between specific waste management operations and adverse health endpoints.

Respiratory Health in Waste Collection and Disposal Workers

Waste management, namely, collection, transport, sorting and processing, and disposal, is an issue of social concern owing to its environmental impact and effects on public health. In fact, waste management activities are carried out according to procedures that can have various negative effects on the environment and, potentially, on human health. The aim of our study was to assess the potential effects on respiratory health of this exposure in workers in the waste management and disposal field, as compared with a group of workers with no occupational exposure to outdoor pollutants. The sample consisted of a total of 124 subjects, 63 waste collectors, and 61 office clerks. Informed consent was obtained from all subjects before inclusion in the study. The entire study population underwent pulmonary function assessments with spirometry and completed two validated questionnaires for the diagnosis of rhinitis and chronic bronchitis. Statistical analyses were performed using STATA 13. Spirometry showed a statistically significant reduction in the mean Tiffenau Index values in the exposed workers, as compared with the controls, after adjusting for the confounding factors of age, BMI, and smoking habit. Similarly, the mean FEV1 values were lower in the exposed workers than in the controls, this difference being again statistically significant. The FVC differences measured in the two groups were not found to be statistically significant. We ran a cross-sectional study to investigate the respiratory health of a group of workers in the solid waste collection and disposal field as compared with a group of office workers. In agreement with most of the data in the literature, our findings support the existence of a prevalence of respiratory deficits in waste disposal workers. Our data suggest the importance of adopting preventive measures, such as wearing specific individual protection devices, to protect this particular category of workers from adverse effects on respiratory health.

Morbidity and mortality of people who live close to municipal waste landfills: a multisite cohort study

BACKGROUND

The evidence on the health effects related to residing close to landfills is controversial. Nine landfills for municipal waste have been operating in the Lazio region (Central Italy) for several decades. We evaluated the potential health effects associated with contamination from landfills using the estimated concentration of hydrogen sulphide (H2S) as exposure.

METHODS

A cohort of residents within 5 km of landfills was enrolled (subjects resident on 1 January 1996 and those who subsequently moved into the areas until 2008) and followed for mortality and hospitalizations until 31 December 2012. Assessment of exposure to the landfill (H2S as a tracer) was performed for each subject at enrolment, using a Lagrangian dispersion model. Information on several confounders was available (gender, age, socioeconomic position, outdoor PM10 concentration, and distance from busy roads and industries). Cox regression analysis was performed [Hazard Ratios (HRs), 95% confidence intervals (CIs)].

RESULTS

The cohort included 242 409 individuals. H2S exposure was associated with mortality from lung cancer and respiratory diseases (e.g. HR for increment of 1 ng/m(3) H2S: 1.10, 95% CI 1.02-1.19; HR 1.09, 95% CI 1.00-1.19, respectively). There were also associations between H2S and hospitalization for respiratory diseases (HR = 1.02, 95% CI 1.00-1.03), especially acute respiratory infections among children (0-14 years) (HR = 1.06, 95% CI 1.02-1.11).

CONCLUSIONS

Exposure to H2S, a tracer of airborne contamination from landfills, was associated with lung cancer mortality as well as with mortality and morbidity for respiratory diseases. The link with respiratory disease is plausible and coherent with previous studies, whereas the association with lung cancer deserves confirmation.

Increased risk of bladder cancer in critical areas at high pressure of pollution of the Campania region in Italy: A systematic review

During the past three decades, large areas of the Naples and the Caserta provinces of the Campania region in Italy have been extensively contaminated by the widespread burial and open-air dumping and incineration of industrial toxic waste. On the basis of the finding that the incidence of bladder cancer appears remarkably high in the Naples province with respect to the rest of Europe and of a potential causative role of environmental contaminants, we sought associations between exposure to toxic agents and increased mortality/incidence of bladder cancer by performing a systematic search of epidemiology and human biomonitoring studies conducted in the provinces of Naples and Caserta. The data show that the incidence of bladder cancer is higher than expected on the basis of regional data in the province of Naples and in certain areas of the province of Caserta, even after accounting for social deprivation, with two clusters of increased mortality rate located in the north-western part of Naples province and in the south-eastern part of the Caserta province. The biomonitoring studies conducted focused on the levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs), which are generated by the uncontrolled combustion of refuse abandoned in the territory and have been shown to enter the food chain. While the average values of PCDD/F and PCBs reported in blood serum and human milk of the area population are in accordance with those expected on the basis of studies conducted at a national and international level, five municipalities assessed in the province of Naples, that is Brusciano, Caivano, Giugliano, Mugnano, and Qualiano-Villaricca were clearly characterized by the presence of arsenic, with 62% samples showing serum arsenic levels higher than the 95th percentile of the national distribution. The potential negative synergism of social deprivation, environmental pressure and arsenic contamination may account for the higher than expected bladder cancer incidence and mortality in certain areas of the Campania region and remains to be elucidated via the conduction of ad hoc population-based studies.

Mortality and morbidity in a population exposed to multiple sources of air pollution: A retrospective cohort study using air dispersion models

BACKGROUND AND AIMS

A landfill, an incinerator, and a refinery plant have been operating since the early 1960s in a contaminated site located in the suburb of Rome (Italy). To evaluate their potential health effects, a population-based retrospective cohort study was conducted using dispersion modeling for exposure assessment.

METHODS

A fixed cohort was enrolled in the Rome Longitudinal Study in 2001, mortality and hospitalizations were followed-up until 2010. Exposure assessments to the landfill (H2S), the incinerator (PM10), and the refinery plant (SOX) were performed for each subject using a Lagrangian dispersion model. Individual and small-area variables were available (including exposures levels to NO2 from traffic and diesel trucks). Cox regression analysis was performed (hazard ratios, HRs, 95% CI) using linear terms for the exposures (5th-95th percentiles difference). Single and bi-pollutant models were run.

RESULTS

The cohort included 85,559 individuals. The estimated annual average exposures levels were correlated. H2S from the landfill was associated with cardiovascular hospital admissions in both genders (HR 1.04 95% CI 1.00-1.09 in women); PM10 from the incinerator was associated with pancreatic cancer mortality in both genders (HR 1.40 95% CI 1.03-1.90 in men, HR 1.47 95% CI 1.12-1.93 in women) and with breast morbidity in women (HR 1.13 95% CI 1.00-1.27). SOx from the refinery was associated with laryngeal cancer mortality in women (HR 4.99 95% CI 1.64-15.9) and respiratory hospital admissions (HR 1.13 95% CI 1.01-1.27).

CONCLUSIONS

We found an association of the pollution sources with some cancer forms and cardio-respiratory diseases. Although there was a high correlation between the estimated exposures, an indication of specific effects from the different sources emerged.

A follow-up of cancer incidence among former Finnish dump site residents: 1999-2011

BACKGROUND

In an analysis of the years 1976-1998, a 50% excess in cancer incidence was observed among residents in twelve blockhouses in Helsinki, Finland on a former dump area containing industrial and household waste.

OBJECTIVE

To assess cancer risk over a 13-year period 1999-2011 among residents formerly living in houses built on a dump area.

METHODS

All 1879 persons who ever lived in the former dump area were identified and the number of cancer cases in this population was obtained from the Finnish Cancer Registry.

RESULTS

After 5 years of residence at the dump site, the standardized incidence ratio of cancer (all sites combined) was 1·32 (95% CI: 0·94-1·79) in men and 0·53 (95% CI: 0·33-0·82) for women, in comparison with the general Helsinki population (1999-2011). No significant excess cancer risks were found.

CONCLUSIONS

Residing on a former dump area was not found to result in an increased risk of cancer.

Health effects associated with the disposal of solid waste in landfills and incinerators in populations living in surrounding areas: a systematic review

OBJECTIVES

Potential health hazards for the environment and people living nearby landfills and incinerators are claimed to be related to several methods of waste management. Independent systematic review of the scientific literature is a key procedure to support the lay public and policy makers to achieve informed decisions.

METHODS

The study design and potential biases of papers retrieved in this comprehensive literature search were analyzed.

RESULTS

The most consistent result is that the risks of congenital anomalies and hospitalization due to respiratory disease are likely to be real nearby special waste landfills. From the very little information on exclusively urban waste depots it is reasonable to say that correct management of landfill does not increase the risk of these health effects. It is confirmed that historically incinerators are an important source of pollution and harm for the health of populations living nearby; however, changes in technology are producing more reassuring results.

CONCLUSIONS

A moderate level of confidence is possible in limited areas of knowledge, implying the need to overcome the limitations of current studies about exposure assessment and to control confounders at the individual level.

Residential proximity to environmental hazards and adverse health outcomes

How living near environmental hazards contributes to poorer health and disproportionate health outcomes is an ongoing concern. We conducted a substantive review and critique of the literature regarding residential proximity to environmental hazards and adverse pregnancy outcomes, childhood cancer, cardiovascular and respiratory illnesses, end-stage renal disease, and diabetes. Several studies have found that living near hazardous wastes sites, industrial sites, cropland with pesticide applications, highly trafficked roads, nuclear power plants, and gas stations or repair shops is related to an increased risk of adverse health outcomes. Government agencies should consider these findings in establishing rules and permitting and enforcement procedures to reduce pollution from environmentally burdensome facilities and land uses.

Health risks in areas close to urban solid waste landfill sites

OBJECTIVE

To evaluate the association between living close to solid waste landfill sites and occurrences of cancer and congenital malformations among populations in their vicinity.

METHODS

Deaths among people living in the municipality of São Paulo, Southeastern Brazil, between 1998 and 2002 were selected and geocoded, according to selected causes. Over the period evaluated, there were 351 deaths due to liver cancer, 160 due to bladder cancer and 224 due to leukemia, among adults, 25 due to childhood leukemia and 299 due to congenital malformation, in areas close to landfill sites. Buffer zones of radius 2 km around the 15 sites delimited the areas exposed. Standardized mortality ratios for each outcome were analyzed in Bayesian spatial models.

RESULTS

In a general manner, the highest values for the standardized mortality ratios were found in more central areas of the municipality, while the landfill sites were located in more peripheral areas. The standardized mortality ratios did not indicate any excess risk for people living in areas close to solid waste landfill sites in the municipality of São Paulo. For landfill sites in operation, there was a greater risk of bladder and liver cancer, and death due to congenital malformation, but without statistical significance.

CONCLUSIONS

No increase in the risk of cancer or congenital malformations was found in areas in the vicinity of urban waste dumps in the municipality of São Paulo. The weak associations and the imprecision of the estimates obtained did not allow any causal relationship to be established.

Waste management health risk assessment: a case study of a solid waste landfill in South Italy

An integrated risk assessment study has been performed in an area within 5 km from a landfill that accepts non hazardous waste. The risk assessment was based on measured emissions and maximum chronic population exposure, for both children and adults, to contaminated air, some foods and soil. The toxic effects assessed were limited to the main known carcinogenic compounds emitted from landfills coming both from landfill gas torch combustion (e.g., dioxins, furans and polycyclic aromatic hydrocarbons, PAHs) and from diffusive emissions (vinyl chloride monomer, VCM). Risk assessment has been performed both for carcinogenic and non-carcinogenic effects. Results indicate that cancer and non-cancer effects risk (hazard index, HI) are largely below the values accepted from the main international agencies (e.g., WHO, US EPA) and national legislation (D.Lgs. 152/2006 and D.Lgs. 4/2008).

Inequalities, inequities, environmental justice in waste management and health

BACKGROUND

The scientific evidence on the health effects of waste-related exposure is not conclusive. Differential exposure to waste by socio-economic status (SES) is often documented, but the interplay between environmental and social factors, crucial for policy making, is not well known. This review aims at investigating the role of health inequalities and inequities in waste management.

METHODS

Grey and peer-reviewed literature, published after 1983, was reviewed from Europe and the USA.

RESULTS

Available data provide consistent indications that waste facilities are often disproportionally more located in areas with more deprived residents, or from ethnical minorities. This applies to waste incinerators, landfills, hazardous waste sites, legal and illegal. In studies considering health effects (mainly from Europe), risks are estimated with standardization for SES. Such standardization almost always decreases risk estimates for several cancers and reproductive outcomes. However, effect modification is not investigated in these studies.

CONCLUSIONS

The patterns of association between waste-related environmental pressures and SES suggest that some of the observed inequalities in exposure and health represent a case of environmental injustice as they are the result of social processes and may be prevented, at least partly. Disentangling the possible health effects remains difficult, due to limitations in the methodology. It seems important to investigate if disadvantaged people are more vulnerable, i.e. risks differ in different social groups living in the same area. Notwithstanding these open questions, public health officers and decision makers should identify waste management policies to minimize their potential health impacts and their unequal distribution.

Systematic review of epidemiological studies on health effects associated with management of solid waste

BACKGROUND

Management of solid waste (mainly landfills and incineration) releases a number of toxic substances, most in small quantities and at extremely low levels. Because of the wide range of pollutants, the different pathways of exposure, long-term low-level exposure, and the potential for synergism among the pollutants, concerns remain about potential health effects but there are many uncertainties involved in the assessment. Our aim was to systematically review the available epidemiological literature on the health effects in the vicinity of landfills and incinerators and among workers at waste processing plants to derive usable excess risk estimates for health impact assessment.

METHODS

We examined the published, peer-reviewed literature addressing health effects of waste management between 1983 and 2008. For each paper, we examined the study design and assessed potential biases in the effect estimates. We evaluated the overall evidence and graded the associated uncertainties.

RESULTS

In most cases the overall evidence was inadequate to establish a relationship between a specific waste process and health effects; the evidence from occupational studies was not sufficient to make an overall assessment. For community studies, at least for some processes, there was limited evidence of a causal relationship and a few studies were selected for a quantitative evaluation. In particular, for populations living within two kilometres of landfills there was limited evidence of congenital anomalies and low birth weight with excess risk of 2 percent and 6 percent, respectively. The excess risk tended to be higher when sites dealing with toxic wastes were considered. For populations living within three kilometres of old incinerators, there was limited evidence of an increased risk of cancer, with an estimated excess risk of 3.5 percent. The confidence in the evaluation and in the estimated excess risk tended to be higher for specific cancer forms such as non-Hodgkin's lymphoma and soft tissue sarcoma than for other cancers.

CONCLUSIONS

The studies we have reviewed suffer from many limitations due to poor exposure assessment, ecological level of analysis, and lack of information on relevant confounders. With a moderate level confidence, however, we have derived some effect estimates that could be used for health impact assessment of old landfill and incineration plants. The uncertainties surrounding these numbers should be considered carefully when health effects are estimated. It is clear that future research into the health risks of waste management needs to overcome current limitations.

Cancer incidence among former Love Canal residents

BACKGROUND

The Love Canal was a rectangular 16-acre, 10-ft-deep chemical waste landfill situated in a residential neighborhood in Niagara Falls, New York. This seriously contaminated site came to public attention in 1978. Only one prior study examined cancer incidence in former residents of the Love Canal neighborhood (LC).

OBJECTIVE

In this study we aimed to describe cancer incidence in former LC residents from 1979 to 1996 and to investigate whether it differs from that of New York State (NYS) and Niagara County (NC).

METHODS

From 1978 to 1982, we interviewed 6,181 former residents, and 5,052 were eligible to be included in this study. In 1996, we identified 304 cancer diagnoses in this cohort using the NYS Cancer Registry. We compared LC cancer incidence with that of NYS and NC using standardized incidence ratios (SIRs), and we compared risks within the LC group by potential exposure to the landfill using survival analysis.

RESULTS

SIRs were elevated for cancers of the bladder [SIR(NYS) = 1.44; 95% confidence interval (CI), 0.91-2.16] and kidney (SIR(NYS) = 1.48; 95% CI, 0.76-2.58). Although CIs included 1.00, other studies have linked these cancers to chemicals similar to those found at Love Canal. We also found higher rates of bladder cancer among residents exposed as children, based on two cases.

CONCLUSIONS

In explaining these excess risks, the role of exposure to the landfill is unclear given such limitations as a relatively small and incomplete study cohort, imprecise exposure measurements, and the exclusion of cancers diagnosed before 1979. Given the relatively young age of the cohort, further surveillance is warranted.

An examination of cancer epidemiology studies among populations living close to toxic waste sites

BACKGROUND

Toxic waste sites contain a broad range of suspected or confirmed human carcinogens, and remain a source of concern to many people, particularly those living in the vicinity of a site. Despite years of study, a consensus has not emerged regarding the cancer risk associated with such sites.

METHODS

We examined the published, peer-reviewed literature addressing cancer incidence or mortality in the vicinity of toxic waste sites between 1980 and 2006, and catalogued the methods employed by such studies.

RESULTS

Nineteen studies are described with respect to eight methodological criteria. Most were ecological, with minimal utilization of hydrogeological or air pathway modeling. Many did not catalogue whether a potable water supply was contaminated, and very few included contaminant measurements at waste sites or in subjects' homes. Most studies did not appear to be responses to a recognized cancer mortality cluster. Studies were highly variable with respect to handling of competing risk factors and multiple comparisons.

CONCLUSION

We conclude that studies to date have generated hypotheses, but have been of limited utility in determining whether populations living near toxic waste sites are at increased cancer risk.

Epidemiologic evidence of relationships between reproductive and child health outcomes and environmental chemical contaminants

This review summarizes the level of epidemiologic evidence for relationships between prenatal and/or early life exposure to environmental chemical contaminants and fetal, child, and adult health. Discussion focuses on fetal loss, intrauterine growth restriction, preterm birth, birth defects, respiratory and other childhood diseases, neuropsychological deficits, premature or delayed sexual maturation, and certain adult cancers linked to fetal or childhood exposures. Environmental exposures considered here include chemical toxicants in air, water, soil/house dust and foods (including human breast milk), and consumer products. Reports reviewed here included original epidemiologic studies (with at least basic descriptions of methods and results), literature reviews, expert group reports, meta-analyses, and pooled analyses. Levels of evidence for causal relationships were categorized as sufficient, limited, or inadequate according to predefined criteria. There was sufficient epidemiological evidence for causal relationships between several adverse pregnancy or child health outcomes and prenatal or childhood exposure to environmental chemical contaminants. These included prenatal high-level methylmercury (CH(3)Hg) exposure (delayed developmental milestones and cognitive, motor, auditory, and visual deficits), high-level prenatal exposure to polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and related toxicants (neonatal tooth abnormalities, cognitive and motor deficits), maternal active smoking (delayed conception, preterm birth, fetal growth deficit [FGD] and sudden infant death syndrome [SIDS]) and prenatal environmental tobacco smoke (ETS) exposure (preterm birth), low-level childhood lead exposure (cognitive deficits and renal tubular damage), high-level childhood CH(3)Hg exposure (visual deficits), high-level childhood exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (chloracne), childhood ETS exposure (SIDS, new-onset asthma, increased asthma severity, lung and middle ear infections, and adult breast and lung cancer), childhood exposure to biomass smoke (lung infections), and childhood exposure to outdoor air pollutants (increased asthma severity). Evidence for some proven relationships came from investigation of relatively small numbers of children with high-dose prenatal or early childhood exposures, e.g., CH(3)Hg poisoning episodes in Japan and Iraq. In contrast, consensus on a causal relationship between incident asthma and ETS exposure came only recently after many studies and prolonged debate. There were many relationships supported by limited epidemiologic evidence, ranging from several studies with fairly consistent findings and evidence of dose-response relationships to those where 20 or more studies provided inconsistent or otherwise less than convincing evidence of an association. The latter included childhood cancer and parental or childhood exposures to pesticides. In most cases, relationships supported by inadequate epidemiologic evidence reflect scarcity of evidence as opposed to strong evidence of no effect. This summary points to three main needs: (1) Where relationships between child health and environmental exposures are supported by sufficient evidence of causal relationships, there is a need for (a) policies and programs to minimize population exposures and (b) population-based biomonitoring to track exposure levels, i.e., through ongoing or periodic surveys with measurements of contaminant levels in blood, urine and other samples. (2) For relationships supported by limited evidence, there is a need for targeted research and policy options ranging from ongoing evaluation of evidence to proactive actions. (3) There is a great need for population-based, multidisciplinary and collaborative research on the many relationships supported by inadequate evidence, as these represent major knowledge gaps. Expert groups faced with evaluating epidemiologic evidence of potential causal relationships repeatedly encounter problems in summarizing the available data. A major driver for undertaking such summaries is the need to compensate for the limited sample sizes of individual epidemiologic studies. Sample size limitations are major obstacles to exploration of prenatal, paternal, and childhood exposures during specific time windows, exposure intensity, exposure-exposure or exposure-gene interactions, and relatively rare health outcomes such as childhood cancer. Such research needs call for investments in research infrastructure, including human resources and methods development (standardized protocols, biomarker research, validated exposure metrics, reference analytic laboratories). These are needed to generate research findings that can be compared and subjected to pooled analyses aimed at knowledge synthesis.

Spatial epidemiology: current approaches and future challenges

Spatial epidemiology is the description and analysis of geographic variations in disease with respect to demographic, environmental, behavioral, socioeconomic, genetic, and infectious risk factors. We focus on small-area analyses, encompassing disease mapping, geographic correlation studies, disease clusters, and clustering. Advances in geographic information systems, statistical methodology, and availability of high-resolution, geographically referenced health and environmental quality data have created unprecedented new opportunities to investigate environmental and other factors in explaining local geographic variations in disease. They also present new challenges. Problems include the large random component that may predominate disease rates across small areas. Though this can be dealt with appropriately using Bayesian statistics to provide smooth estimates of disease risks, sensitivity to detect areas at high risk is limited when expected numbers of cases are small. Potential biases and confounding, particularly due to socioeconomic factors, and a detailed understanding of data quality are important. Data errors can result in large apparent disease excess in a locality. Disease cluster reports often arise nonsystematically because of media, physician, or public concern. One ready means of investigating such concerns is the replication of analyses in different areas based on routine data, as is done in the United Kingdom through the Small Area Health Statistics Unit (and increasingly in other European countries, e.g., through the European Health and Environment Information System collaboration). In the future, developments in exposure modeling and mapping, enhanced study designs, and new methods of surveillance of large health databases promise to improve our ability to understand the complex relationships of environment to health.

Health and environment information systems for exposure and disease mapping, and risk assessment

A large number of chemicals are used on a regular basis in modern society. Thousands of new chemicals are added each year, many of which may have toxic properties constituting potential health hazards. Rapid assessment of the risk associated with the use of these chemicals is therefore essential to protect people from exposure to potentially harmful substances. Exposures to chemicals (and physical agents) are typically unevenly distributed geographically as well as temporally. Disease occurrence also shows geographically varying patterns. Geographic information systems (GIS) may be used to produce maps of exposure and/or disease to reveal spatial patterns. Exposure mapping using advanced GIS modeling may enhance exposure assessment in environmental epidemiology studies. Disease maps can be valuable tools in risk assessment to explore changes in disease patterns potentially associated with changes in environmental exposures. Spatial variations in risk and trends related to distance from pollution sources may be studied using software tools such as the Rapid Inquiry Facility, developed by the U.K. Small Area Health Statistics Unit and enhanced in the European Health and Environment Information System project, for an initial quick evaluation of any potential health hazards associated with an environmental pollutant.

Solid waste disposal in urban areas and health--the case of Belo Horizonte, Brazil

The presence of sanitary or controlled landfill in urban areas and its implications for the health of the population that lives in its bordering area has been little investigated. The presence of these deposits, with design or operational problems, can end up providing a likely location for the proliferation of diverse vectors and favouring uncontrolled emissions, which may affect health, both for the people that work and live in these places and those that live nearby. This paper describes a study carried out in the city of Belo Horizonte, Brazil, with the objective of associating the presence of the BR 040 sanitary landfill, located in the urban environment, and the health of the neighbouring population. There were 475 possibilities of occurrences studied, covering 19 different combinations for association between the exposure factor and the groupings of researched diseases (respiratory diseases, diarrhoea and skin diseases). However, of this total only 33 results were shown to be significant in showing the existence of an association. For these results, the variable exposures identified as a risk factor showed an odds ratio ranging between 1.20 and 13.75. Although without an evidenced relationship, respiratory diseases appeared as a relevant outcome in the study, as they were present in 23 of the 33 studied combinations in which the results were significant.