Mortality among Paris sewage workers

Occupational health outcomes among sanitation workers: A systematic review and meta-analysis

BACKGROUND

Sanitation workers are essential to global public health and societal wellbeing. However, the health risks and outcomes associated with exposure to occupational risk factors among sanitation workers are neither well understood nor well quantified. We undertook a systematic review to (1) identify occupational risk factors among sanitation workers and (2) assess the effect of occupational exposure to human fecal sludge and wastewater on selected health outcomes among these workers.

METHODS

We searched four databases (i.e., PubMED, MEDLINE, EMBASE, and LILACS) for eligible studies from inception through to January 01, 2020. The included population was workers ≥15 years engaged, formally or informally, in installing, operating, servicing, cleaning or emptying a sanitation technology at any step of the sanitation chain. The included comparator was workers in other occupations or the general population. Eligible outcomes were: mortality (any or all causes), gastroenteritis, occupational injuries, respiratory diseases, musculoskeletal disorders, and mental and social health conditions. Risk of bias was assessed separately on exposure assessment and health outcome using a modified Liverpool Quality Assessment Tool (LQAT). We pooled sufficiently homogenous studies using inverse variance meta-analysis with random effects.

RESULTS

A total of 65 studies (9 cohort studies, 56 cross-sectional studies) met the inclusion criteria. One quarter of studies (n = 15) were from middle-income countries. Few studies assessed occupational risk factor exposures directly; most assigned exposure via proxy of occupation of sanitation worker. We judged nearly all studies to have "high risk of bias" in exposure and outcome assessment. Despite these limitations, the consistency of the overall evidence suggests that sanitation workers are at increased risk of gastroenteritis and respiratory conditions, and may be at increased risk of musculoskeletal disorders and mental/social health conditions. The pooled odds ratio for hepatitis A--the only outcome deemed suitable for meta-analysis--was 2.09 (95% Predicted Interval: 1.39-3.00, 12 studies). There was conflicting evidence from studies of increased risk of mortality; only one study reported on injuries.

CONCLUSION

Despite a large number of studies, there is limited evidence to date of the health risks faced by sanitation workers, particularly among groups that may be at particular risk-- women, informal workers and those living in low-income countries. Nevertheless, the research to date provides suggestive evidence of elevated occupational risk among sanitation workers across a range of health condition. More research is needed to improve the current bodies of evidence for all included health outcomes to be able to quantify disease burden among this occupational group.

Current status of agricultural soil pollution by heavy metals in China: A meta-analysis

In the last decades, agricultural soil pollution by heavy metals has been extensively investigated in China. However, nearly all studies were field monitoring in small regions and/or with limited samples, which may not represent soil pollution situation at the national scale. In this paper, attempt was made to provide a comprehensive report about heavy metal pollution in China based on meta-analysis of reviewed data. Given the characteristics of field monitoring studies, the weighted mean values based on "sampling number", "study area", and "standard deviation" were calculated to represent national mean values. In addition, subgroup analysis and cumulative meta-analysis were applied to explore the spatial and temporal variations as well as the influence of cropping systems. 336 articles published from 2005 to 2017 were reviewed in the analysis. Eight heavy metals (cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), arsenic (As), copper (Cu), zinc (Zn) and nickel (Ni)) were analyzed. The contents of Cd and Hg were increased compared to background values, while, other six elements showed no significant accumulation. Little pollution was found in normal farmland, which was far from obvious anthropogenic emissions, but Cd and Hg in mining & smelting areas and industrial areas continued to accumulate significantly. Moreover, the accumulation had slowed down or decreased since 2012, which might be due to reduced use of coals, non-ferrous metals and agro-chemicals. Heavy metal contents were generally higher in southwest and south coastal areas but lower in northwest regions, whereas vegetable and paddy fields had higher concentrations than upland and other land use. This study provides information on soil pollution caused by heavy metals and its affected regions and cropping systems on a national scale. It can be useful for developing heavy metal pollution control and management strategies in China.

Impacts of soil and water pollution on food safety and health risks in China

Environmental pollution and food safety are two of the most important issues of our time. Soil and water pollution, in particular, have historically impacted on food safety which represents an important threat to human health. Nowhere has that situation been more complex and challenging than in China, where a combination of pollution and an increasing food safety risk have affected a large part of the population. Water scarcity, pesticide over-application, and chemical pollutants are considered to be the most important factors impacting on food safety in China. Inadequate quantity and quality of surface water resources in China have led to the long-term use of waste-water irrigation to fulfill the water requirements for agricultural production. In some regions this has caused serious agricultural land and food pollution, especially for heavy metals. It is important, therefore, that issues threatening food safety such as combined pesticide residues and heavy metal pollution are addressed to reduce risks to human health. The increasing negative effects on food safety from water and soil pollution have put more people at risk of carcinogenic diseases, potentially contributing to 'cancer villages' which appear to correlate strongly with the main food producing areas. Currently in China, food safety policies are not integrated with soil and water pollution management policies. Here, a comprehensive map of both soil and water pollution threats to food safety in China is presented and integrated policies addressing soil and water pollution for achieving food safety are suggested to provide a holistic approach.

Mortality analysis on wastewater exposure in Shijiazhuang, Hebei, China, from 2007 to 2011

The study investigated the age-adjusted mortality rate and disease odds among deceased residents living in areas exposed to wastewater and cleanwater from 2007 to 2011, in Shijiazhuang, China. Mortality data for eight villages exposed to wastewater and 16 villages not exposed to wastewater were collected and crosschecked from multiple sources. Overall mean age-adjusted mortality rate for wastewater areas was 798/105 (95% Confidence Interval (CI) = ± 68), insignificantly higher than the mean mortality rate for cleanwater area, 726/105 (95% CI = ± 46), p > 0.05. Malignant neoplasms and respiratory mortality and disease odds were higher in wastewater areas than in cleanwater areas, OR = 1.7 (95% CI = 1.3-2.2, p < 0.01) and OR = 1.9 (95% CI = 1.1-3.4, p < 0.05), respectively. Wastewater area mortality and disease odds for Lung and Stomach cancers after adjustments were OR = 1.6 (95% CI = 1.1-2.4, p < 0.05) and OR = 1.8 (95% CI = 1.2-2.7, p < 0.01), respectively, significantly higher than those of cleanwater areas. There is a possibility that exposure to wastewater might be associated with cancer and respiratory disease mortality. The study recommends that the use of wastewater be limited, discouraged, or discontinued.

Integrated exposure assessment of sewage workers to genotoxicants: an urinary biomarker approach and oxidative stress evaluation

BACKGROUND

Sewage workers are exposed to multiple chemicals among which many are suspected genotoxicants. Therefore, they might incur DNA damage and oxidative stress. We aimed to explore integrated urinary biomarkers, assessing the overall urine genotoxicity by in vitro comet and micronucleus assays and measuring urinary 8-oxo-2'-deoxyguanosine.

METHODS

During three consecutive working days, polycyclic aromatic hydrocarbons and volatile organic compounds were sampled in workplace air of 34 sewage and 30 office workers, as indicators of airborne exposure. The last day, subjects collected their 24 hours urine. Genotoxicity of urinary extracts was assessed by comet and micronucleus assays on a HepG2 cell line. Using competitive enzymatic immunoassay we evaluated the 24 hours urinary 8-oxo-2'-deoxyguanosine excretion. Benzo(a)pyrene toxicity equivalent factors and inhalation unit risk for Benzo(a)pyrene and benzene were used to give an estimate of cancer risk levels.

RESULTS

Workplace air concentrations of polycyclic aromatic hydrocarbons (e.g. 23.7 [range 2.4-104.6] ng.m-3 for fluoranthene) and volatile organic compounds (e.g. 19.1 ± 2.9 [standard error] μ.m-3 for benzene) were elevated in sewage compared to office workplaces (P < 0.01) and corresponded to an increased lifetime cancer risk. The urinary extracts of sewage workers showed higher genotoxicity (P < 0.001) than office workers.

CONCLUSIONS

The integrated and non-specific urinary biomarkers of exposure showed that sewage workers experience exposure to mixtures of genotoxicants in the workplace.

Cognitive functions changes among Egyptian sewage network workers

The current work aimed at investigating the cognitive functions impairment among workers of sewer networks due to exposure to hydrogen sulfide (H(2)S) and the relation of this impairment, if any, to the level of H(2)S exposure biomarker 'urinary thiosulfate.' Besides, the validity of using Mini Mental State Examination (MMSE) as screening test for cognitive impairment among the exposed workers was tested. The work was conducted among 33 sewage network maintenance male workers and a matched unexposed control group (n = 30). The participants were subjected to clinical neurological history, estimation of urinary thiosulfate, and assessment of cognitive dysfunction by using neurophysiological (simple reaction time, P300 test) and neuropsychological tests (Wechsler Memory Scale) and frontal executive functions tests. Clinical neurological history revealed significantly higher neurological symptoms (headache, memory defects, lack of concentration) among exposed workers compared to their controls (p < 0.05). Exposed workers had significantly prolonged simple reaction time and delayed P300 latency and showed poor performance of most of neuropsychological tests. Marked elevation of urinary thiosulfate was observed among the exposed workers (p < 0.001) but this elevation was not correlated with the duration of exposure or any of the other measured parameters. Exposed workers had significantly lower mean value of MMSE scoring than that of the controls (p < 0.001). In conclusion, exposure to H( 2)S among sewer network workers is associated with cognitive impairment, which can be screened by applying MMSE as a simple rapid test for H( 2)S occupationally exposed workers.

Cancer incidence in the wastewater treatment plant of a large chemical company

OBJECTIVES

To evaluate cancer incidence among employees assigned to BASF's wastewater treatment plant.

METHODS

We conducted a retrospective cohort study including 477 male employees who had ever worked in the facility for at least 1 year since the start of operations in 1974. Cancers were identified by review of occupational medical records and a standardized questionnaire completed by the participants or their next of kin. Confirmation through hospital records was sought for all reported cases after obtaining informed consent. Standardized incidence ratios (SIR) and 95% confidence intervals (CI) were computed using comparison data provided by the Saarland Cancer Registry. Further comparisons were made between three different subgroups of employees, working in maintenance, wastewater processing, and sewage sludge treatment.

RESULTS

A total of 50 cancers were observed (SIR 1.14, CI 0.85-1.51). Colorectal (1.14, 0.42-2.48), bronchial (1.40, 0.67-2.57) and prostate (1.15, 0.42-2.50) were the most frequently observed cancers. Five cases of bladder cancer were found in the total cohort (1.75, 0.57-4.09), with four of them occurring in the sewage sludge treatment area (6.82, 1.86-17.46). Allowing for a 10-year lag did not significantly change the results.

CONCLUSIONS

The overall cancer experience among employees of the wastewater treatment plant was similar to that of the corresponding general population. The finding of an excess risk for bladder cancer in one subgroup of workers was unexpected with regard to the available literature. There is no straightforward explanation for this finding, and it may be due to chance. An extended follow-up of this cohort will take place after 5 years. Annual bladder cancer screening is offered to active and retired employees from this plant for the time being. The current working conditions and work practices have been re-assessed by occupational hygienists and deemed to be safe.

Biomonitoring of complex occupational exposures to carcinogens: the case of sewage workers in Paris

Background

Sewage workers provide an essential service in the protection of public and environmental health. However, they are exposed to varied mixtures of chemicals; some are known or suspected to be genotoxics or carcinogens. Thus, trying to relate adverse outcomes to single toxicant is inappropriate. We aim to investigate if sewage workers are at increased carcinogenic risk as evaluated by biomarkers of exposure and early biological effects.

Methods/design

This cross sectional study will compare exposed sewage workers to non-exposed office workers. Both are voluntaries from Paris municipality, males, aged (20–60) years, non-smokers since at least six months, with no history of chronic or recent illness, and have similar socioeconomic status. After at least 3 days of consecutive work, blood sample and a 24-hour urine will be collected. A caffeine test will be performed, by administering coffee and collecting urines three hours after. Subjects will fill in self-administered questionnaires; one covering the professional and lifestyle habits while the a second one is alimentary. The blood sample will be used to assess DNA adducts in peripheral lymphocytes. The 24-hour urine to assess urinary 8-oxo-7, 8-dihydro-2'-deoxy-Guanosine (8-oxo-dG), and the in vitro genotoxicity tests (comet and micronucleus) using HeLa S3 or HepG2 cells. In parallel, occupational air sampling will be conducted for some Polycyclic Aromatic Hydrocarbons and Volatile Organic Compounds. A weekly sampling chronology at the offices of occupational medicine in Paris city during the regular medical visits will be followed. This protocol has been accepted by the French Est III Ethical Comitee with the number 2007-A00685-48.

Discussion

Biomarkers of exposure and of early biological effects may help overcome the limitations of environmental exposure assessment in very complex occupational or environmental settings.