Direct Contamination Research Articles

Bioactive contaminants of emerging concern in National Park waters of the northern Colorado Plateau, USA

Pharmaceuticals and personal care products (PPCPs), wastewater indicators (WWIs), and pesticides (herein, Contaminants of Emerging Concern [CECs]) have been documented in surface waters throughout the world and have associated risks to aquatic life. While much research has focused on temperate and urbanized watersheds, less is known about CEC presence in semi-arid landscapes, where water availability is limited and populations are low. CEC presence in water and sediment is reported for 21 sites in eight U.S. national parks in the northern Colorado Plateau region. From 2012 to 2016, at least one PPCP and/or WWI was detected at most sites on over half of sampling visits, indicating that CECs are not uncommon even in isolated areas. CEC detections were generally fewer and at lower concentrations than in urbanized or agricultural watersheds. Consistent with studies from other U.S. regions, the most frequently detected CECs in this study include DEET, caffeine, organophosphorus flame retardants, and bisphenol A in water and fecal indicators and polycyclic aromatic hydrocarbons in sediment. Maximum concentrations in this study were generally below available water quality benchmarks, sediment quality guidelines, and risk assessment thresholds associated with vertebrates. Additional work is needed to assess the potential activity of hormones, which had high reporting limits in our study, and potential bioactivity of environmental concentrations for invertebrates, microbial communities, and algae. Potential sources of CEC contamination include upstream wastewater effluent discharges and National Park Service invasive-plant-control herbicide applications. CEC occurrence patterns and similarities between continuous and isolated flow locations suggest that direct contamination from individual visitors may also occur. While our data indicate there is little aquatic health risk associated with CECs at our sites, our results demonstrate the ubiquity of CECs on the landscape and a continued need for public outreach concerning resource-use ethics and the potential effects of upstream development.

Outbreak of Invasive Wound Mucormycosis in a Burn Unit Due to Multiple Strains of Mucor circinelloides f. circinelloides Resolved by Whole-Genome Sequencing.

ABSTRACTMucorales are ubiquitous environmental molds responsible for mucormycosis in diabetic, immunocompromised, and severely burned patients. Small outbreaks of invasive wound mucormycosis (IWM) have already been reported in burn units without extensive microbiological investigations. We faced an outbreak of IWM in our center and investigated the clinical isolates with whole-genome sequencing (WGS) analysis. We analyzed M. circinelloides isolates from patients in our burn unit (BU1, Hôpital Saint-Louis, Paris, France) together with nonoutbreak isolates from Burn Unit 2 (BU2, Paris area) and from France over a 2-year period (2013 to 2015). A total of 21 isolates, including 14 isolates from six BU1 patients, were analyzed by whole-genome sequencing (WGS). Phylogenetic classification based on de novo assembly and assembly free approaches showed that the clinical isolates clustered in four highly divergent clades. Clade 1 contained at least one of the strains from the six epidemiologically linked BU1 patients. The clinical isolates were specific to each patient. Two patients were infected with more than two strains from different clades, suggesting that an environmental reservoir of clonally unrelated isolates was the source of contamination. Only two patients from BU1 shared one strain, which could correspond to direct transmission or contamination with the same environmental source. In conclusion, WGS of several isolates per patients coupled with precise epidemiological data revealed a complex situation combining potential cross-transmission between patients and multiple contaminations with a heterogeneous pool of strains from a cryptic environmental reservoir.

Aliphatic hydrocarbon biomarkers as indicators of organic matter source and composition in surface sediments from shallow lakes along the lower Yangtze River, Eastern China

Aliphatic hydrocarbon biomarkers from the surface sediments of lakes along the lower reaches of the Yangtze River (Eastern China) were analyzed in order to determine the origin and composition of organic matter (OM) in the sediment. This is necessary to understand how anthropogenic environmental change in the region is impacting on OM dynamics and carbon cycles. The results indicate that OM in lake sediments is derived from biogenic sources, including phytoplankton, aquatic macrophytes, bacteria and terrestrial plants and abiotic sources of petroleum hydrocarbon contamination. The significance of each source varies greatly between lakes. Inputs of autochthonous OM to sediments were closely dependent on nutrient levels and the organisms present in the lake water column. Cyanobacterial OM input, signified by the distribution of short-chain n-alkanes, was most abundant in sediments from the most severely polluted lake, West Lake Chaohu. OM derived from diatoms, indicated by C25 highly branched isoprenoids (HBIs), was relatively abundant in sediments from lakes Gucheng and Shijiu, the two studied lakes with the lowest nutrient levels. Growth of macrophytes in lakes Gucheng, Shijiu, Gehu and Yangcheng resulted in a significant accumulation of OM from these organisms in the sediments. In contrast, the input of allochthonous OM was controlled mainly by natural and anthropogenic activities around the lakes. For example, terrestrial plant OM input, deduced from the abundance and proportion of long-chain n-alkanes, was exceptionally high in the sediment of Lake Nanyi, perhaps stemmed from frequent severe flooding in the catchment. Input of fossil fuel OM reflected direct petroleum contamination of the water or anthropogenic petroleum burning in the catchment. In addition, the allochthonous refractory OM tended to be enriched in sediments of lakes with strong hydrodynamic process. The results of this study provided a lot of detail in explaining the variation of terrestrial OM dynamics and carbon cycle in response to anthropogenic activities.

Can Methicillin-resistant Staphylococcus aureus Silently Travel From the Gut to the Wound and Cause Postoperative Infection? Modeling the "Trojan Horse Hypothesis".

To determine whether intestinal colonization with methicillin-resistant Staphylococcus aureus (MRSA) can be the source of surgical site infections (SSIs). We hypothesized that gut-derived MRSA may cause SSIs via mechanisms in which circulating immune cells scavenge MRSA from the gut, home to surgical wounds, and cause infection (Trojan Horse Hypothesis). MRSA gut colonization was achieved by disrupting the microbiota with antibiotics, imposing a period of starvation and introducing MRSA via gavage. Next, mice were subjected to a surgical injury (30% hepatectomy) and rectus muscle injury and ischemia before skin closure. All wounds were cultured before skin closure. To control for postoperative wound contamination, reiterative experiments were performed in mice in which the closed wound was painted with live MRSA for 2 consecutive postoperative days. To rule out extracellular bacteremia as a cause of wound infection, MRSA was injected intravenously in mice subjected to rectus muscle ischemia and injury. All wound cultures were negative before skin closure, ruling out intraoperative contamination. Out of 40 mice, 4 (10%) developed visible abscesses. Nine mice (22.5%) had MRSA positive cultures of the rectus muscle without visible abscesses. No SSIs were observed in mice injected intravenously with MRSA. Wounds painted with MRSA after closure did not develop infections. Circulating neutrophils from mice captured by flow cytometry demonstrated MRSA in their cytoplasm. Immune cells as Trojan horses carrying gut-derived MRSA may be a plausible mechanism of SSIs in the absence of direct contamination.

Microbiome Medicine: This Changes Everything

Microbiome Medicine: This Changes Everything

Radiation protection from external exposure to radionuclides: A Monte Carlo data handbook

The availability of a resource collecting dose factors for the evaluation of the absorbed doses from external exposure during the manipulation of radioactive substances is fundamental for radiological protection purposes. Monte Carlo simulations are useful for the accurate calculation of dose distributions in complex geometries, particularly in presence of extended spectra of multi-radiation sources. We considered, as possible irradiation scenarios, a point source, a uniform planar source resembling a contaminated surface, several source volumes contained in plastic or glass receptacles, and the direct skin contamination case, implementing the corresponding Monte Carlo simulations in GAMOS (GEANT4-based Architecture for Medicine-Oriented Simulations). A set of 50 radionuclides was studied, focusing the attention on those ones mainly used in nuclear medicine, both for diagnostic and therapeutic purposes, in nuclear physics laboratories and for instrument calibration. Skin dose equivalents at 70 μm of depth and deep dose equivalents at 10 mm of depth are reported for different configurations and organized in easy-to-read tables.

Use of ultraviolet-fluorescence-based simulation in evaluation of personal protective equipment worn for first assessment and care of a patient with suspected high-consequence infectious disease

Variations currently exist across the UK in the choice of personal protective equipment (PPE) used by healthcare workers when caring for patients with suspected high-consequence infectious diseases (HCIDs). To test the protection afforded to healthcare workers by current PPE ensembles during assessment of a suspected HCID case, and to provide an evidence base to justify proposal of a unified PPE ensemble for healthcare workers across the UK. One 'basic level' (enhanced precautions) PPE ensemble and five 'suspected case' PPE ensembles were evaluated in volunteer trials using 'Violet'; an ultraviolet-fluorescence-based simulation exercise to visualize exposure/contamination events. Contamination was photographed and mapped. There were 147 post-simulation and 31 post-doffing contamination events, from a maximum of 980, when evaluating the basic level of PPE. Therefore, this PPE ensemble did not afford adequate protection, primarily due to direct contamination of exposed areas of the skin. For the five suspected case ensembles, 1584 post-simulation contamination events were recorded, from a maximum of 5110. Twelve post-doffing contamination events were also observed (face, two events; neck, one event; forearm, one event; lower legs, eight events). All suspected case PPE ensembles either had post-doffing contamination events or other significant disadvantages to their use. This identified the need to design a unified PPE ensemble and doffing procedure, incorporating the most protective PPE considered for each body area. This work has been presented to, and reviewed by, key stakeholders to decide on a proposed unified ensemble, subject to further evaluation.

Iatrogenic implantation of myxoid dedifferentiated chondrosarcoma at donor site: A case report and review of literature

AbstractIatrogenic implantation of chondrosarcoma (CS) is not only extremely rare but also technically avoidable and impacts with morbidity, mortality, and quality of life (QoL). We report a similar case of myxoid dedifferentiated CS at remote tissue-graft donor site (left chest-wall pectoralis major myocutaneous flap). Although the exact mechanism of primary tumor cells seeding is not clear, the probable causes are direct contamination from surgical instruments and altered blood circulation at the graft-donor site.

Human prion diseases: current issues

Prion diseases, or transmissible spongiform encephalopathies, are a group of neurodegenerative diseases with progressive dementia and movement disorders. There are three variants of prion diseases pathogenesis: direct contamination, genetic and sporadic forms. The following clinical forms are known: Creutzfeldt-Jakob disease (common type), variant Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker disease, variably protease-sensitive prionopathy, fatal insomnia and fatal familial insomnia, kuru, prion disease associated with diarrhea and autonomic neuropathy. Clinical characteristic of prion diseases, molecular-genetic aspects of their pathogenesis and current diagnostic approaches are discussed. Because of the lack of effective treatment, prevention of both alimentary prion infections (consumption of contaminated meat products) and transmissible iatrogenic infections (the use of biopreparations from animal tissues) is important. The safety of such biopreparations should be ensured by modern manufacturing technologies and specially developed procedures that meet international requirements and standards.

The Effects of Lead Contamination in Public Health Case: Pesarean Village, Tegal District, Indonesia

Lead is one of the ten main chemicals that was found naturally in the earth's crust and has toxic effects to human health. Direct contamination due to the re-suspension of dust containing lead from soil can be inhaled by certain environmental conditions, for example in dry season and enter human body directly. The aim of this study was analyzing the effect of lead contamination toward human health in Pasarean Village.The research was conducted in Pesarean Village, Tegal District where metal smelting and used lead acid battery smelting had been done in more than 10 years ago and left the waste aside as an open dumping waste. The method that was used in this study were qualitative method using questionnaire and reviewing secondary data which was supported with literature reviews. The result showed that almost 80% of people has acute and chronic symptoms of lead poisoning and it showed that lead contained in blood was high or exceeding the blood lead level standard in human.

Utilisation of visible/near-infrared hyperspectral images to classify aflatoxin B1 contaminated maize kernels

A visible/near-infrared (VNIR) hyperspectral imaging (HSI) system (400–1000 nm) was used to assess the feasibility of detecting aflatoxin B1 (AFB1) on surfaces of 600 kernels of four maize varieties from different regions of the U.S.A. i.e. Georgia, Illinois, Indiana and Nebraska. For each variety, four AFB1 solutions (10, 20, 100 and 500 ppb) were artificially applied on kernel surfaces. Similarly, a control group was generated from 30 kernels of each variety treated with a solution of methanol. Principal component analysis (PCA) was used to reduce dimensionality of the HSI data followed by the application of factorial discriminant analysis (FDA) on the principal component variables. PCA results showed a pattern of separation between uncontaminated and contaminated kernels for all varieties except for Indiana and pooled samples. FDA showed the ability to predict AFB1 contamination of each variety with over 96% validation accuracy while prediction for AFB1 contamination group membership of pooled samples reached 98% accuracy in validation. Variation in the spectra of AFB1 contaminated kernels could have caused the variation in the predicted AFB1 contamination group membership. The PCA and FDA models where influenced by the chemical information from C H, N H and O H bonds of VNIR spectral regions. This study presents the potential of using VNIR hyperspectral imaging in direct AFB1 contamination classification studies of maize kernels of different varieties. The study further suggests that varietal differences of maize kernels may have no influence on AFB1 contamination classification.

Direct and Indirect Anthropogenic Contamination in Water Sources: Evaluation of Chromosomal Stability and Cytotoxicity Using the Allium cepa Test.

Increasing industrialization and urbanization has deteriorated water quality around the world. Nowadays, evaluation of the effects of chemical compounds using bioassays is a critical step in the hazard identification assessment. Thus, this work aimed to determine the genetic damage caused by different types of anthropogenic contamination in a river´s water in Brazil. Two points (P1 and P2) and two periods (referred as direct and indirect anthropogenic contamination) were evaluated in Allium cepa roots. MI was increased (p < 0.05) in both points in the indirect anthropogenic contamination and decreased in theindirect anthropogenic contamination periods. Moreover, parameters as DNA instability (CA and MN) were observed in both periods indicating substances in the water with mutagenic, genotoxic, and cytotoxic potential. Interestingly, a 20-fold increase in CA frequencies were observed in P1 and P2 in the second collection period (direct anthropogenic contamination) (p < 0.05). In conclusion, our data indicated that anthropogenic activities in the area contributed to contaminate this water source. Moreover, direct anthropogenic contamination maximized the damage, posing a possible hazard to population health.

Estimation of chromium and copper in chicken liver samples by Inductively Coupled plasma–Optical Emission Spectrometry method

Due to food safety issues and human health risk, heavy metal concentration through food chain is a concerned problem worldwide. There are several reports on transfer of non-biodegradable heavy metals from soil to animals by direct contamination or through feed. Hence, the present study was undertaken to estimate the presence of heavy metals chromium and copper in chicken liver samples (n=54) which were collected in and around Tirupati region of Andhra Pradesh, India. These samples were analyzed for the presence of chromium and copper by using Inductively Coupled Plasma–Optical Emission Spectrometer (ICP-OES). The excess levels of chromium considered to be carcinogenic and copper leads to tissue injury. The results of this study revealed that the range of chromium is between 0.009 to 0.091ppm and for Copper is 0.006 to 2.54 ppm in chicken liver samples which is not significant and within prescribed tolerance limit.

Collateral contamination concomitant to the polonium-210 poisoning of Mr Alexander Litvinenko

Mr Litvinenko died on 23 November 2006, having been poisoned with polonium-210 on 1 November, with evidence of a previous poisoning attempt during October 2006. Measurements of 210Po in urine samples were made for a large number of people to determine whether they may have been contaminated. In the majority of cases, measured levels were attributable to the presence of 210Po from normal dietary sources. For a small number of cases, elevated levels provided evidence of direct contamination associated with the poisonings. For one individual, while estimated doses were below thresholds for irreversible organ damage, a notably increased risk of cancer can be inferred. The use of the chelating agent, unithiol, to increase 210Po excretion in this case was only moderately effective in reducing doses received.

Abstract 5315: Dietary intake and risk of lung cancer in non-smoking women: a hospital-based case-control study in Xuanwei and Fuyuan, China

Abstract Xuanwei and Fuyuan are rural counties in China that have the highest lung cancer rates in the country among non-smoking women. This alarming public health burden has been attributed to the combustion of smoky (bituminous) coal for heating and cooking, which can produce carcinogenic emissions such as polycyclic aromatic hydrocarbons (PAHs). Previous studies found that green leafy vegetables could absorb PAHs through air and direct soil contamination. Further, oral ingestion of PAHs was found be to associated with pulmonary adenoma development in animal feeding studies. Therefore, we investigated the associations between lung cancer risk and dietary intake of specific green leafy vegetables and other foods in non-smoking women of this farming region. We conducted a hospital-based case-control study of 1,074 female lung cancer patients and 977 frequency-matched controls from Xuanwei and Fuyuan, China in 2006-2013. Dietary intake was self-reported on questionnaires and categorized as never, several times/year, several times/month, several times/week, and every day. Unconditional logistic regression models were used to estimate the odds ratios (OR) and 95% confidence intervals (CI) of lung cancer in relation to intake of specific green leafy vegetables (i.e. lettuce, cabbage, fennel, spinach, hollow vegetables), corn, buckwheat, carrots, tomatoes, dried and fresh chili, pickled vegetables, bean curd, mushrooms, and preserved meats. Models were adjusted for age, county, first-degree relative with lung cancer, passive smoke exposure, education, lifetime smoky coal tonnage, respiratory disease history, time spent indoors, and menopausal status. Separate models were fitted for each dietary factor. We found that increased consumption of several green leafy vegetables was associated with increased risk of lung cancer. Eating hollow vegetables every day was associated with 2.50 (95% CI: 1.18, 5.27) times the odds of lung cancer compared to never. Similarly, eating lettuce (OR=2.13, 95% CI: 1.41, 3.21) and cabbage (OR=1.82, 95% CI: 1.21, 2.69) every day was associated with increased risks compared to several times a year or less. Conversely, eating bean curd (OR=0.54, 95% CI: 0.40, 0.72) several times a week was associated with decreased risk compared to several times a year or less; while eating buckwheat (OR=0.59, 95% CI: 0.40, 0.89) several times a week was associated with decreased risk compared to never. No significant associations were found for fennel, spinach, and other foods. Our findings suggest that increased consumption of a variety of green leafy vegetables may be related to elevated lung cancer risk in non-smoking women from Xuanwei and Fuyuan, China, independent of other risk factors. The increased risk may be due to environmental contamination of crops from coal combustion. Conversely, frequent consumption of bean curd and buckwheat was found to be protective. Citation Format: Jason Y. Wong, Bryan A. Bassig, Wei Hu, Jinming Zhang, Wei Jie Seow, Neil E. Caporaso, Bu-tian Ji, Robert S. Chapman, George S. Downward, Jihua Li, Jun He, Kaiyun Yang, Yunchao Huang, Roel Vermeulen, Nathaniel Rothman, Qing Lan. Dietary intake and risk of lung cancer in non-smoking women: a hospital-based case-control study in Xuanwei and Fuyuan, China [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5315. doi:10.1158/1538-7445.AM2017-5315

Ecotoxicity of two organic UV-filters to the freshwater caddisfly Sericostoma vittatum

Organic ultraviolet filters (UV-filters) used for protection against radiation in personal care products and other materials (e.g. textiles, plastic products) are considered emerging contaminants of aquatic ecosystem. Benzophenone-3 (BP3) and 3-(4-methylbenzylidene)camphor (4-MBC) are the most commonly used organic UV-filters and have been reported in freshwater environments due to contamination through discharges from wastewater treatment plants and swimming pools or by direct contamination from recreational activities. Our aim was to evaluate the ecotoxicological effects of these UV-filters using the freshwater caddisfly Sericostoma vittatum’ biochemical biomarkers and energy processing related endpoints (feeding behaviour, energy reserves and cellular metabolism). In laboratory trials, both compounds induced feeding inhibition of S. vittatum at 3.55 mg/kg of BP3 and at concentrations ≥2.57 mg/kg of 4-MBC, decreased carbohydrates content at 3.55 and 6.95 mg/kg of BP3 and 4-MBC respectively, and increased total glutathione levels at concentrations ≥1.45 and 1.35 mg/kg of BP3 and 4-MBC respectively. No significant effects were observed on endpoints associated with oxidative stress, antioxidant defences, phase II biotransformation or neurotoxicity after exposure to the two UV-filters. Our results show that environmental relevant concentrations of BP3 and 4-MBC, can negatively impact freshwater insects and demonstrate the importance of monitoring the ecological effects of organic UV-filters using non-model invertebrate species.

Ornamental plants on sale to the public are a significant source of pesticide residues with implications for the health of pollinating insects

Garden centres frequently market nectar- and pollen-rich ornamental plants as “pollinator-friendly”, however these plants are often treated with pesticides during their production. There is little information on the nature of pesticide residues present at the point of purchase and whether these plants may actually pose a threat to, rather than benefit, the health of pollinating insects. Using mass spectrometry analyses, this study screened leaves from 29 different ‘bee-friendly’ plants for 8 insecticides and 16 fungicides commonly used in ornamental production. Only two plants (a Narcissus and a Salvia variety) did not contain any pesticide and 23 plants contained more than one pesticide, with some species containing mixtures of 7 (Ageratum houstonianum) and 10 (Erica carnea) different agrochemicals. Neonicotinoid insecticides were detected in more than 70% of the analysed plants, and chlorpyrifos and pyrethroid insecticides were found in 10% and 7% of plants respectively. Boscalid, spiroxamine and DMI-fungicides were detected in 40% of plants. Pollen samples collected from 18 different plants contained a total of 13 different pesticides. Systemic compounds were detected in pollen samples at similar concentrations to those in leaves. However, some contact (chlorpyrifos) and localised penetrant pesticides (iprodione, pyroclastrobin and prochloraz) were also detected in pollen, likely arising from direct contamination during spraying. The neonicotinoids thiamethoxam, clothianidin and imidacloprid and the organophosphate chlorpyrifos were present in pollen at concentrations between 6.9 and 81 ng/g and at levels that overlap with those known to cause harm to bees. The net effect on pollinators of buying plants that are a rich source of forage for them but simultaneously risk exposing them to a cocktail of pesticides is not clear. Gardeners who wish to gain the benefits without the risks should seek uncontaminated plants by growing their own from seed, plant-swapping or by buying plants from an organic nursery.

Dental Unit Water Lines and their Disinfection and Management: A Review.

The perceived threat to public health from dental unit water line (DUWL) contamination comes from opportunistic and respiratory pathogens such as Legionella spp, Nontuberculous Mycobacteria (NTM) and pseudomonads. These organisms can grow and multiply in the DUWL biofilm to reach infective concentrations, with the potential for inhalation leading to respiratory infections or direct contamination of surgical wounds. In this paper we discuss current legislation and practical methods for delivering water within the DUWL that meets the standards for safety. Clinical relevance: Understanding the clinical relevance and methods for decontaminating DUWL is essential to create a safe working environment in dentistry.

English

The potential of two entomopathogenic fungi Metarhizium anisopliae.and Beauveria bassiana for the control of Coelaemenodera elaeidis were evaluated. The objective of this study was to control C. elaeidis using entomopathogenic fungi as biocontrol agents. The pathogenicity of M. anisopliae and B. bassiana isolates were tested using direct contamination bioassay set up of 2.5 g conidia (2.5 g of Metarhizium 2.5 x 1010 or 2.5g of Beauveria 1011) transferred to the centre of plastic Petri dishes. Results from M. anisopliae studies indicated that C. elaeidis changed from yellow to brown and darker brown colour. Death of C. elaeidis was observed on the fourth day post incubation with 100% mortality and the control treatment recorded 14% mortality. C. elaeidis were observed with white mycelia growth on the ninth day, the green conidia appeared around the cadavers. Using B. bassiana, ingestion of spores caused infection from the mandible which spread to the thorax. Infection spread beneath the thorax colonizing the abdomen with white mycelia growth.&nbsp; Death was observed on C. elaeidis with 100% mortality on the sixth day post incubation. The larvae and pupae recorded deaths on the eighth and eleventh days post incubations with 100% each. The control treatment recorded mortalities at 21% for larvae and 7% for pupae. The study results indicated that both M. anisopliae and B. bassiana have a high potential as biocontrol agents for the control of C. elaeidis. Key words: Biocontrol, mortality, Coelaemenodera elaeidis, M. anisopliae, B. bassiana

Worldwide Regulatory Guidance Values Applied to Direct Contact Surface Soil Pesticide Contamination: Part I—Carcinogenic Pesticides

Regulatory agencies worldwide have developed regulatory guidance values (RGVs) for nearly 800 pesticides. Analysis of the residential surface soil guidance values applied to the most frequently regulated current-use agriculture, home, and garden pesticides is presented. Part I concentrates on values applied to atrazine, simazine, and trifluralin. These are unique among commonly used pesticides because they are generally considered to be human carcinogens. Their use has been banned in much of the world, but they are commonly used in the United States. Regulatory guidance values applied to these 3 pesticides vary by 8.6, 5.5, and 5.1 orders of magnitude. Risk model coefficient–bounded set uncertainty analysis is applied to help analyze this variability. Cancer risk model uncertainty bounds appear to contain 36.3%, 43.0%, and 49.5% of the RGVs. Most of the remaining values appear to exceed a lifetime cancer incidence risk of 1 × 10−6 and may not be adequately protective of human health.