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Epidemiology
Published in Samuel C. Morris, Cancer Risk Assessment, 2020
An example of how an extrapolated dose-response function can give an inaccurate prediction of cancer risk and how epidemiology can resolve the discrepancy was mentioned earlier. Pike et al. (1975) applied their dose-response function extrapolated from gas retort workers to explain an increase in lung cancer found in an ecological study in areas of Los Angeles with high BaP levels. In a subsequent case-control study, the same group was able to account for essentially all of excess cancer risk by considering occupational exposure in the petrochemical industry which was producing the high ambient levels (Pike et al., 1979). Although the authors concluded that this could not completely eliminate the possibility that air pollution caused some increased lung cancer, the environmental exposure could no longer be considered the principal cause of the excess cancers. One possibility is that the different qualitative mix in the Los Angeles air produced a different, and much lower, relationship with the BaP index; another is that the linear extrapolation used is not correct and that the effect is less per unit dose at lower dose rates. The findings cast doubt on the validity of all of the POM dose-response fuctions discussed above when applied to ambient exposure levels. Additional validation studies of this kind are needed to confirm the findings of this single study.
Chronic Arsenic Exposure to Drinking Water
Published in M. Manzurul Hassan, Arsenic in Groundwater, 2018
With an ecological study for lung cancer mortality statistics during the period 1973–1986 of residents and levels of arsenic concentrations in four townships in the BFD-endemic area in Taiwan, Wu et al. (1989) showed that age-adjusted SMR for lung cancer increased with increasing concentrations of arsenic in well water for residents aged 20 years or older. An ecological analysis during 1973–1986 in the BFD-endemic area by Chen et al. (1992) observed significantly elevated ratios for lung cancer mortality associated with high arsenic concentrations (≥600 μg/L compared to <100 μg/L) among both males (RR: 2.42) and females (RR: 3.90). With the information of cancer death occurring between 1986 and 1993 in a study population of 263 BFD-patients and 2293 healthy subjects in Taiwan, Chiou et al. (1995) found a statistically significant positive association between ingested inorganic arsenic (0–1140 μg/L) and cancer of the lung and bladder. Analyzing the cohort with urine samples and arsenic exposure in the BFD-endemic area of Taiwan during an average follow-up period of 17.8 years and 193 subjects with all-site cancer deaths, Chung et al. (2013b) observed 71 (37%) deaths from lung cancer.
A distributed lag non-linear time-series study of ambient temperature and healthcare-associated infections in Hefei, China
Published in International Journal of Environmental Health Research, 2023
Yile Wu, Mingming Liang, Qiwei Liang, Xiyao Yang, Yehuan Sun
This study provided evidence of the exposure-lag-response association between ambient temperature and HAIs, which will attract the attention of researchers to the effects of climate variables on HAIs. Healthcare institutions and hospital infection management departments should consider the impacts of meteorological factors when taking measures to reduce HAIs. Nevertheless, several limitations must be acknowledged. First, this time-series analysis was an ecological study, and thus, an ecological fallacy might exist. Second, the sample in this study was limited to a single hospital, albeit a large, comprehensive, tertiary-care hospital in the area, therefore, the findings should be interpreted with caution when generalized to other regions. This may also be the reason that the correlation between temperature and HAIs was not statistically significant in the subgroup analyses. Third, the confounding effects of indoor environment were not investigated. However, the dynamics of indoor environmental conditions, human occupancy, and operational characteristics of buildings in healthcare settings might influence human comfort or survival of microbial communities, which could impact the spread of HAIs (Ramos et al. 2015).
Critical review on PFOA, kidney cancer, and testicular cancer
Published in Journal of the Air & Waste Management Association, 2021
Scott M. Bartell, Verónica M. Vieira
Human studies of PFAS and cancer were summarized in a recent scoping review, which identified 28 published primary studies on the topic (Steenland and Winquist 2021). Among these studies, those that examined PFOA and kidney cancer are listed in Table 1, and those that examined PFOA and testicular cancer are listed in Table 2. Because it is a major determinant of the statistical precision and power of each study, as well as the ability to evaluate dose-response trends, the studies were listed in order by the number of cancer cases included, with the largest case numbers first. Some studies used additional data from external groups for comparison, but only those cases used in internal dose-response analyses were included here. This ordering reflects only the likely impacts of case counts on sampling variability, and should not be confused with study quality or reliability; for example, the study listed first in Table 1 (Mastrantonio et al. 2018) had the largest number of kidney cancer deaths, but relatively weak ascertainment of exposure, and an ecological study design allowing only group-level assessment of most variables. Three cohort studies reported positive but non-significant associations between PFOA and testicular cancer mortality with only 1 testicular cancer death (Gilliland and Mandel 1993; Leonard et al. 2008; Steenland and Woskie 2012), and were excluded from Table 2 due to an insufficient sample size.