Hearing Loss and Urinary trans,trans-Muconic Acid (t,t-MA) in 6- to 19-Year-Old Participants of NHANES 2017-March 2020.

Hearing loss (HL) is associated with poorer language development and school performance. Ototoxic substances such as metals and solvents, including benzene, are a risk factor associated with HL. This study examines potential associations between the benzene metabolite trans,trans-muconic acid (t,t-MA) and HL in youth of the National Health and Nutrition Examination Survey (NHANES). Logistic regression calculated adjusted odds ratio (aOR) associations between HL and urinary t,t-MA quartiles, natural-log transformed, and doubled urinary t,t-MA. Hearing threshold pure-tone average (PTA) at speech frequencies (SF) 0.5, 1, 2, and 4 kHz and high frequencies (HF) 3, 4, and 6 kHz were analyzed for slight HL (PTA > 15 dB) and mild HL (PTA > 20 dB). Urinary t,t-MA was statistically significantly associated with both slight SF and HF HL. For each doubling of t,t-MA there were increased odds of having slight SFHL (aOR = 1.42; 95% CI: 1.05, 1.92), slight HFHL (aOR = 1.31; 95% CI: 1.03, 1.66), mild SFHL (aOR = 1.60; 95% CI: 1.10, 2.32), and mild HFHL (aOR = 1.45; 95% CI: 1.03, 2.04). To our knowledge, this is the first population-based report of an association between SFHL, HFHL, and the benzene metabolite t,t-MA in youth 6 to 19 years old.

Safe Listening at Venues and Events with Amplified Music - United States, 2022.

Nearly one in four (24.4%) U.S. adults aged 20-69 years show evidence of noise-induced hearing loss (1). Among those reporting exposure to noise outside of work, 19.9% showed possible noise-induced hearing loss. Exposure to non-job-related noise can be substantial (2). Loud music from personal listening devices and entertainment venues might place more than 1 billion teenagers and young adults at risk for hearing loss worldwide (3). Early noise exposure might increase the risk for age-related hearing loss later in life (4). CDC analyzed data from the 2022 FallStyles survey (conducted by Porter Novelli via the Ipsos' KnowledgePanel) on U.S. adult perceptions regarding preventing hearing loss from amplified music at venues or events. More than one half of U.S. adults agreed with one or more of the following protective actions: limiting sound levels, posting warning signs, and using hearing protection when music at such events reaches potentially hazardous levels. Hearing and other health professionals can make use of existing materials available from the World Health Organization (WHO), CDC, and other professional organizations to raise awareness about noise risks and promote protective behaviors.

Survey of Teen Noise Exposure and Efforts to Protect Hearing at School - United States, 2020.

Noise-induced hearing loss (NIHL) is a substantial, often unrecognized, health problem. Various learning environments and activities in school settings are loud. Researchers have reported the prevalence of NIHL among U.S. adolescents ranging between 12.8% and 17.5%, suggesting that one in every six to eight middle and high school students (aged 12-19 years) has measurable hearing loss likely resulting from excessive noise exposure (1). Evidence suggests that even mild levels of hearing loss negatively affect auditory perception and cognitive skills.* CDC analyzed data from a sample of 817 youths aged 12-17 years who responded to the web-based YouthStyles survey in 2020. The survey measured the frequency of exposure to loud noise in school settings, the provision of hearing protection devices (HPDs) during exposure, and whether prevention techniques were part of their educational curriculum. Approximately three in four teenage students reported being exposed to loud sound at school, and nearly one half (46.5%) of respondents reported exposure to loud sounds at school on a regular basis. A majority of students (85.9%) reported that their school did not provide HPDs during classes or activities where they were exposed to loud sounds, and seven out of 10 reported they were never taught how to protect their hearing. Increasing youth's awareness about the adverse health effects of excessive noise exposure and simple preventive measures to reduce risk can help prevent or reduce NIHL. Health care providers and educators have resources and tools available to prevent NIHL among school-aged children. Increased efforts are needed to promote prevention.

Perfluoroalkyl acids, hyperuricemia and gout in adults: Analyses of NHANES 2009-2014.

BACKGROUND: Previous studies have reported a positive association of perfluoralkyl acids (PFAAs), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), with hyperuricemia. The objective of the study is to investigate whether there is an association between concurrent serum levels of several PFAAs and gout, serum uric acid (SUA) or hyperuricemia in the U.S. adult population as represented by the National Health and Nutrition Examination Survey (NHANES) 2009-2014 sample (n = 4917). The PFAAs investigated include PFOA, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS) and PFOS. METHODS: This cross-sectional study used multivariate logistic regressions to analyze the association of single PFAAs with hyperuricemia and self-reported gout; the association with SUA was analyzed by multivariate linear regression. Analyses were adjusted for race/ethnicity, age, sex, education, alcohol consumption, smoking, serum cotinine, BMI, diabetes, hypertension, chronic kidney disease, and SUA (for gout only). RESULTS: Higher quartile values of serum PFOA and PFHxS were associated with increased odds of self-reported gout. There was a positive association of SUA with increased levels of PFOA, PFNA, PFOS, PFHxS and PFDA. Higher quartile values of PFOA, PFNA, and PFHxS were associated with higher odds of hyperuricemia. CONCLUSIONS: In this population-based cross-sectional analysis, we found an association between selected PFAAs and self-reported gout. We also confirmed previous reports of an association between several PFAAs and hyperuricemia. Our study suggests that exposure to PFAAs may be a risk factor for hyperuricemia and gout.

Perfluoroalkyl substances and anthropomorphic measures in children (ages 3-11 years), NHANES 2013-2014.

BACKGROUND: Perfluoroalkyl acids (PFAAs) are man-made compounds that are persistent in the environment and highly bioaccumulative in the body. Humans are exposed to a mixture of these substances, and the effects of these mixtures may be different than the effects noted for individual compounds. Prenatal exposure to PFAAs has been associated with decreased birth weight. The objective of the present study is to evaluate concurrent serum PFAA levels, as single compounds and as mixtures, in relation to anthropomorphic measures in children. METHODS: Using multivariate linear regression, we evaluated the association between single or PFAA mixtures and with height-for-age (HAZ), weight-for-age (WAZ), and BMI (BMIZ) z-scores in children (ages 3-11 years) participants of the National Health and Nutrition Examination Survey (NHANES) 2013-2014. Analyses were also stratified by sex. The PFAA mixture was based on relative potency factors express in terms of PFOA equivalency (CmixRPFi) or as molar sum of the PFAA congeners (∑molPFAA). RESULTS: There was a statistically significant association of PFHxS and PFOS with decreased HAZ in boys. The significantly decreased HAZ in boys was also found when the PFAAs were analyzed as mixtures: CmixRPFi (ß = -0.33; 95%CI: 0.63, -0.04) or ΣmolPFAAs (ß = -0.30; 95%CI: 0.56, -0.04). In boys, PFHxS was also associated with decreased WAZ and BMIZ. The only statistically significant association found in girls was between decreased HAZ and PFHxS. CONCLUSIONS: We found sex differences in the association between concurrent serum PFAA levels and anthropomorphic measures in children 3-11 years old. PFAA levels, as single congeners or as mixture concentrations were associated with decreased height-for-age z-score in boys.

Association of Obesity with Hearing Impairment in Adolescents.

Hearing loss (HL) is the third most common chronic physical condition in the United States. Obesity has become an increasingly important public health concern, as the prevalence in children, adolescents and adults has increased over the past few decades. The objectives of this study is to investigate whether obesity is associated with audiometric notches indicative of noise-induced hearing loss (NIHL), speech frequency hearing loss (SFHL), and high frequency hearing loss (HFHL) in adolescent participants of the National Health and Nutrition Examination Survey 2007-2010. The prevalence of overall audiometric notches in the adolescent population was 16.0% with higher prevalence in females than males. The prevalence of SFHL and HFHL were higher in males than females (SFHL, 7.3% vs. 5.4%, respectively; and HFHL 14.3% vs. 8.1%, respectively). Obese adolescents had a higher adjusted OR to have audiometric notches (OR = 1.93; 95% CI: 1.33-2.81) and HFHL (OR = 1.95; 95% CI: 1.19-3.21). Continued preventative efforts towards reducing obesity might also help to reduce the risk for HL and NIHL.

Age and sex differences in hearing loss association with depressive symptoms: analyses of NHANES 2011-2012.

BACKGROUND: Depression is a common and significant health problem. Hearing loss is the third most common chronic physical condition in the USA and might be a factor in depression. To determine whether hearing loss is associated with depressive symptoms in US adults ages 20-69 years. METHODS: National Health and Nutrition Examination Survey (NHANES) data (2011-2012) were used to assess the potential relationship between hearing loss and depression, in adults (20-69 years) who answered the Patient Health Questionnaire (PHQ-9) depression screening module, with pure tone audiometry measurements, and complete information on the co-variates data (n = 3316). The degree of speech-frequency hearing loss (SFHL) and high-frequency hearing loss (HFHL) were defined as slight/mild hearing loss ⩾26-40 dB; moderate/worse hearing loss ⩾41 dB by pure tone audiometry examination. RESULTS: Moderate/worse HFHL was statistically significantly associated with depressive symptoms (OR 1.54, 95% CL 1.04-2.27) when the analyses were conducted among all participants. Further stratification by gender and age groups found that moderate/worse HFHL (OR 3.85, 95% CL 1.39-10.65) and moderate/worse SFHL (OR 5.75, 95% CL 1.46-22.71) were associated with depressive symptoms in women ages 52-69 years. CONCLUSIONS: Moderate/worse speech frequency and HFHL are associated with depression in women ages 52-69 years, independent of other risk factors. Hearing screenings are likely to reduce delays in diagnosis and provide early opportunities for noise prevention counseling and access to hearing aids. Health professionals should be aware of depressive signs and symptoms in patients with hearing loss.

Use of Personal Hearing Protection Devices at Loud Athletic or Entertainment Events Among Adults - United States, 2018.

Tens of millions of U.S. residents have a range of adverse health outcomes caused by noise exposure (1). During 2011-2012, 21 million U.S. adults who reported no exposure to loud or very loud noise at work exhibited hearing damage suggestive of noise-induced hearing loss (2). In addition to the known risk for hearing damage, nonauditory adverse health outcomes and health risks from excessive environmental sound exposure can include effects on the cardiovascular system, metabolism, blood pressure, body weight, cognition, sleep, mental health, quality of life, and overall well-being (1,3,4). CDC analyzed a representative sample of the U.S. adult population (aged ≥18 years) from a 2018 national marketing survey (50 states and the District of Columbia) that included questions about use of hearing protection devices (HPDs) (e.g., ear plugs or ear muffs) during recreational exposure to loud athletic and entertainment events; approximately 8% of respondents reported consistent use of an HPD at these types of events. Among those adults more likely to wear an HPD, 63.8% had at least some college education, and 49.1% had higher income levels. Women and older adults were significantly less likely to use HPDs. These findings suggest a need to strengthen a public health focus on the adverse health effects of excessive noise exposure at home and in recreational settings as well as a need for continued efforts to raise public awareness about the protective value of HPDs.

Antimony and sleep-related disorders: NHANES 2005-2008.

BACKGROUND: Antimony is used as a flame-retardant in textiles and plastics, in semiconductors, pewter, and as pigments in paints, lacquers, glass and pottery. Subacute or chronic antimony poisoning has been reported to cause sleeplessness. The prevalence of short sleep duration (<7h/night) has been reported to be 37.1% in the general US population, and obstructive sleep apnea (OSA) affects 12-28 million US adults. Insufficient sleep and OSA have been linked to the development of several chronic conditions including diabetes, cardiovascular disease, obesity and depression, conditions that pose serious public health threats. OBJECTIVE: To investigate whether there is an association between antimony exposure and sleep-related disorders in the US adult population using the National Health and Nutrition Examination Survey (NHANES) 2005-2008. METHODS: We performed multivariate logistic regression to analyze the association of urinary antimony with several sleep disorders, including insufficient sleep and OSA, in adult (ages 20 years and older) participants of NHANES 2005-2008 (n=2654). RESULT: We found that participants with higher urinary antimony levels had higher odds to experience insufficient sleep (≤6h/night) (OR 1.73; 95%CI; 1.04, 2.91) as well as higher odds to have increased sleep onset latency (>30min/night). Furthermore, we found that higher urinary antimony levels in participants were associated with OSA (OR 1.57; 95%CI; 1.05, 2.34), sleep problems, and day-time sleepiness. CONCLUSION: In this study, we found that urinary antimony was associated with higher odds to have insufficient sleep and OSA. Because of the public health implications of sleep disorders, further studies, especially a prospective cohort study, are warranted to evaluate the association between antimony exposure and sleep-related disorders.

Vital Signs: Noise-Induced Hearing Loss Among Adults - United States 2011-2012.

INTRODUCTION: The 2016 National Academies of Sciences report "Hearing Health Care for Adults: Priorities for Improving Access and Affordability" included a call to action for government agencies to strengthen efforts to collect, analyze, and disseminate population-based data on hearing loss in adults. METHODS: CDC analyzed the most recent available data collected both by questionnaire and audiometric tests of adult participants aged 20-69 years in the 2011-2012 National Health and Nutrition Examination Survey (NHANES) to determine the presence of audiometric notches indicative of noise-induced hearing loss. Prevalence of both unilateral and bilateral audiometric notches and their association with sociodemographics and self-reported exposure to loud noise were calculated. RESULTS: Nearly one in four adults (24%) had audiometric notches, suggesting a high prevalence of noise-induced hearing loss. The prevalence of notches was higher among males. Almost one in four U.S. adults who reported excellent or good hearing had audiometric notches (5.5% bilateral and 18.0% unilateral). Among participants who reported exposure to loud noise at work, almost one third had a notch. CONCLUSIONS AND IMPLICATIONS FOR PUBLIC HEALTH PRACTICE: Noise-induced hearing loss is a significant, often unrecognized health problem among U.S. adults. Discussions between patients and personal health care providers about hearing loss symptoms, tests, and ways to protect hearing might help with early diagnosis of hearing loss and provide opportunities to prevent harmful noise exposures. Avoiding prolonged exposure to loud environments and using personal hearing protection devices can prevent noise-induced hearing loss.

Cadmium, Lead, and Depressive Symptoms: Analysis of National Health and Nutrition Examination Survey 2011-2012.

BACKGROUND: Several studies have noted an association between tobacco smoke and depression. Cadmium and lead are neurotoxicant components of tobacco smoke. The objective of the present study is to investigate the potential association between blood cadmium (BCd) and blood lead (BPb) with current depressive symptoms in the US adult population. METHODS: We conducted cross-sectional analyses of adult participants (≥ 20 years) from the National Health and Nutrition Examination Survey 2011-2012 (N = 3,905). Multivariate logistic regressions were used to analyze the association between BCd and BPb with depressive symptoms; analyses were also stratified on sex and age groups (20-47 years and ≥ 48 years). Presence or absence of depressive symptoms was determined using the Patient Health Questionnaire module. RESULTS: Individuals in the highest quartile of BCd had higher odds of having depressive symptoms (odds ratio = 1.68; 95% confidence limits: 1.12, 2.51). This association was found only in male participants and, more specifically, in younger adult male participants (20-47 years). We found that BPb, cigarette smoking, and obesity were associated with depressive symptoms in younger female adults. CONCLUSIONS: In this study, we report associations between BCd and BPb with current depressive symptoms that were modified by age and sex. Reverse causation cannot be ruled out as a possible explanation since depression may lead to behavioral changes that increase exposure to cadmium and lead (ie, tobacco smoke). The continued efforts at reducing cadmium through tobacco smoking cessation programs may decrease the prevalence of current depressive symptoms.

Serum Testosterone Concentrations and Urinary Bisphenol A, Benzophenone-3, Triclosan, and Paraben Levels in Male and Female Children and Adolescents: NHANES 2011-2012.

BACKGROUND: Exposure to environmental phenols (e.g., bisphenol A, benzophenone-3, and triclosan) and parabens is widespread in the population. Many of these chemicals have been shown to have anti-androgenic effects both in vitro and in vivo. OBJECTIVE: We examined the association of bisphenol A (BPA), benzophenone-3 (BP-3), triclosan (TCS), and parabens with serum total testosterone (TT) levels in child and adolescent participants (ages 6-19 years) in the National Health and Nutrition Examination Survey (NHANES) 2011-2012. METHODS: We performed multivariable linear regression to estimate associations between natural log-transformed serum TT and quartiles of urinary BPA, BP-3, TCS, and parabens in male and female children (ages 6-11 years) and adolescents (ages 12-19 years). RESULTS: BP-3 and BPA were associated with significantly lower TT in male adolescents, and BPA was associated with significantly higher TT in female adolescents. TT was not consistently associated with TCS or total parabens in children or adolescents of either sex. CONCLUSIONS: To our knowledge, this is the first study to report an association of both BP-3 and BPA with serum TT in adolescents. Associations between BPA and TT differed according to sex in adolescents, with inverse associations in boys and positive associations in girls. BP-3 was associated with significantly lower TT in adolescent boys only. However, because of the limitations inherent to the cross-sectional study design, further studies are needed to confirm and elucidate on our findings. Citation: Scinicariello F, Buser MC. 2016. Serum testosterone concentrations and urinary bisphenol A, benzophenone-3, triclosan, and paraben levels in male and female children and adolescents: NHANES 2011-2012. Environ Health Perspect 124:1898-1904; http://dx.doi.org/10.1289/EHP150.

Urinary antimony and leukocyte telomere length: An analysis of NHANES 1999-2002.

Telomeres are repetitive DNA sequences (TTAGGG) at the end of chromosomes. Cells with critically short telomeres enter replicative senescence and apoptosis. Several in vitro studies report that antimony causes cell apoptosis in human leukocyte cell lines. The goal of this analysis was to investigate whether there is an association between antimony exposure and leukocyte telomere length (LTL) among US adults aged 20 and older based on the National Health and Nutrition Examination Survey (NHANES) 1999-2002. We used multivariate linear regression to analyze the association of urinary antimony with LTL. LTL was log-natural transformed and the results were re-transformed and presented as percent differences. After adjustment for potential confounders, individuals in the 3rd and 4th quartiles of urinary antimony had statistically significantly shorter LTL (-4.78%, 95% CI: -8.42,-0.90; and -6.11%, 95% CI: -11.04,-1.00, respectively) compared to the lowest referent quartile, with evidence of a dose-response relationship (p-value for trend =0.03). Shorter LTL with antimony was driven by middle aged (40-59 years) and older (60-85 years) adult groups. The association may be biologically plausible because of reported oxidative stress and apoptosis effects of antimony on blood cells, effects known to shorten telomere length.

Urinary Phthalates and Leukocyte Telomere Length: An Analysis of NHANES 1999-2002.

The International Agency for Research on Cancer classified the di-2-ethylhexyl phthalate (DEHP) as "possibly carcinogenic to humans". In vitro studies reported that phthalate exposure resulted in induction of several nuclear transcription factors that are activators of telomerase reverse transcriptase (TERT) and telomerase activity of the human telomerase complex. The objective of this study was to determine whether there is an association between urinary phthalate metabolites [mono-ethyl phthalate (MEP), mono-butyl phthalate (MBP), mono-(2-ethyl)-hexyl phthalate (MEHP), and mono-benzyl phthalate (MBzP) and leukocyte telomere length (LTL) in the adult population of the National Health and Nutrition Examination Survey (NHANES) 1999-2002 (n=2472). After adjustment for potential confounders, participants in the 3rd and 4th quartiles of urinary MEHP had statistically significantly longer LTL (5.34%, 95% CI: 1.31, 9.53; and 7.14%, 95% CI: 2.94, 11.63; respectively) compared to the lowest quartile, with evidence of a dose-response relationship (p-trend=0.01). The association remained when the analyses were stratified by age groups (20-39years, 40-59years, and 60years and older), and sex. Furthermore, MBP and MBzP were associated with higher LTL in older participants. The age independent association between longer LTL and MEHP (a metabolite of DEHP) might suggest a possible role of MEHP as tumor promoter.

Acrolein metabolites, diabetes and insulin resistance.

Acrolein is a dietary and environmental pollutant that has been associated in vitro to dysregulate glucose transport. We investigated the association of urinary acrolein metabolites N-acetyl-S-(3-hydroxypropyl)-l-cysteine (3-HPMA) and N-acetyl-S-(carboxyethyl)-l-cysteine (CEMA) and their molar sum (∑acrolein) with diabetes using data from investigated 2027 adults who participated in the 2005-2006 National Health and Nutrition Examination Survey (NHANES). After excluding participants taking insulin or other diabetes medication we, further, investigated the association of the compounds with insulin resistance (n=850), as a categorical outcome expressed by the homeostatic model assessment (HOMA-IR>2.6). As secondary analyses, we investigated the association of the compounds with HOMA-IR, HOMA-ß, fasting insulin and fasting plasma glucose. The analyses were performed using urinary creatinine as independent variable in the models, and, as sensitivity analyses, the compounds were used as creatinine corrected variables. Diabetes as well as insulin resistance (defined as HOMA-IR>2.6) were positively associated with the 3-HPMA, CEMA and ∑Acrolein with evidence of a dose-response relationship (p<0.05). The highest 3rd and 4th quartiles of CEMA compared to the lowest quartile were significantly associated with higher HOMA-IR, HOMA-ß and fasting insulin with a dose-response relationship. The highest 3rd quartile of 3-HPMA and ∑Acrolein were positively and significantly associated with HOMA-IR, HOMA-ß and fasting insulin. These results suggest a need of further studies to fully understand the implications of acrolein with type 2 diabetes and insulin.

Urinary and blood cadmium and lead and kidney function: NHANES 2007-2012.

BACKGROUND: Cadmium (Cd) and lead (Pb) are widespread environmental contaminants that are known nephrotoxins. However, their nephrotoxic effects at low-environmental exposure levels are debated. OBJECTIVE: We examined the association of blood Pb (B-Pb), blood Cd (B-Cd), urinary Pb (U-Pb) and urinary Cd (U-Cd) with estimated glomerular filtration rate (eGFR) and urinary albumin (ALB). METHODS: We used multivariate linear regression to analyze the association between B-Pb, B-Cd, U-Pb, and U-Cd with eGFR and ALB in adult participants (≥20 years of age) in NHANES 2007-2012. The dataset was limited to NHANES individuals with both blood and urinary metal measurements. RESULTS: We found a statistically significant inverse association between eGFR and B-Cd and statistically significant positive associations between eGFR and both U-Cd and U-Pb, as well as statistically significant associations between ALB and the 3rd and 4th quartiles of U-Cd. CONCLUSIONS: The inverse association between eGFR and B-Cd, in conjunction with positive associations between eGFR and ALB with U-Cd, suggest that U-Cd measurement at low levels of exposure may result from changes in renal excretion of Cd due to kidney function and protein excretion. However, renal effects such as hyperfiltration from Cd-mediated kidney damage or creatinine-specific Cd effects cannot be excluded with this cross-sectional design.

Perfluoroalkyl substances and food allergies in adolescents.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of organic compounds that are persistent in the environment due to their stable carbon-fluorine backbone, which is not susceptible to degradation. Research suggests these chemicals may exert an immunotoxic effect. The aim of this study is to investigate the associations between four PFASs - perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS) - with food sensitization and food allergies in adolescent participants (ages 12-19years) in the National Health and Nutrition Examination Survey (NHANES) 2005-2006 and 2007-2010, respectively. We performed multivariate logistic regression to analyze the association between individual PFASs with food sensitization (defined as having at least 1 food-specific IgE level≥0.35kU/L) in NHANES 2005-2006 and food allergies (self-reported) in NHANES 2007-2010. Serum PFOA, PFOS, and PFHxS were statistically significantly associated with higher odds to have self-reported food allergies in NHANES 2007-2010. When using IgE levels as a marker of food sensitization, we found that serum PFNA was inversely associated with food sensitization (NHANES 2005-2006). In conclusion, we found that serum levels of PFASs were associated with higher odds to have self-reported food allergies. Conversely, adolescents with higher serum PFNA were less likely to be sensitized to food allergens. These results, along with previous studies, warrant further investigation, such as well-designed longitudinal studies.

A simple procedure for estimating pseudo risk ratios from exposure to non-carcinogenic chemical mixtures.

Non-cancer risk assessment traditionally assumes a threshold of effect, below which there is a negligible risk of an adverse effect. The Agency for Toxic Substances and Disease Registry derives health-based guidance values known as Minimal Risk Levels (MRLs) as estimates of the toxicity threshold for non-carcinogens. Although the definition of an MRL, as well as EPA reference dose values (RfD and RfC), is a level that corresponds to "negligible risk," they represent daily exposure doses or concentrations, not risks. We present a new approach to calculate the risk at exposure to specific doses for chemical mixtures, the assumption in this approach is to assign de minimis risk at the MRL. The assigned risk enables the estimation of parameters in an exponential model, providing a complete dose-response curve for each compound from the chosen point of departure to zero. We estimated parameters for 27 chemicals. The value of k, which determines the shape of the dose-response curve, was moderately insensitive to the choice of the risk at the MRL. The approach presented here allows for the calculation of a risk from a single substance or the combined risk from multiple chemical exposures in a community. The methodology is applicable from point of departure data derived from quantal data, such as data from benchmark dose analyses or from data that can be transformed into probabilities, such as lowest-observed-adverse-effect level. The individual risks are used to calculate risk ratios that can facilitate comparison and cost-benefit analyses of environmental contamination control strategies.