The contribution of epidemiology

Risk assessment of nutrients: There must be a threshold for their effects

Nutrients serve physiological functions in a dose-dependent manner and that needs to be recognized in risk assessment. An example of the consequences of not properly considering this can be seen in a recent assessment by the European Food Safety Authority (EFSA). EFSA concluded in 2022 that the intake of added and free sugars should be "as low as possible in the context of a nutritionally adequate diet". That conclusion of EFSA is based on the effects on two surrogate endpoints for an adverse effect found in randomized controlled trials with high sugars intake levels: fasting glucose and fasting triglycerides. The lowest intake levels in these trials were around 10 energy% and at this intake level there were no adverse effects on the two outcomes. This indicates that the adverse effects of sugars have an observable threshold value for these two endpoints. The most appropriate interpretation from the vast amount of data is that currently no definitive conclusion can be drawn on the tolerable upper intake level for dietary sugars. Therefore, EFSA's own guidance would lead to the conclusion that the available data do not allow the setting of an upper limit for added sugars and hence, that more robust data are required to identify the threshold value for intake of sugars.

Scientific Opinion of the PPR Panel on the follow-up of the findings of the External Scientific Report 'Literature review of epidemiological studies linking exposure to pesticides and health effects'

In 2013, EFSA published a comprehensive systematic review of epidemiological studies published from 2006 to 2012 investigating the association between pesticide exposure and many health outcomes. Despite the considerable amount of epidemiological information available, the quality of much of this evidence was rather low and many limitations likely affect the results so firm conclusions cannot be drawn. Studies that do not meet the 'recognised standards' mentioned in the Regulation (EU) No 1107/2009 are thus not suited for risk assessment. In this Scientific Opinion, the EFSA Panel on Plant Protection Products and their residues (PPR Panel) was requested to assess the methodological limitations of pesticide epidemiology studies and found that poor exposure characterisation primarily defined the major limitation. Frequent use of case-control studies as opposed to prospective studies was considered another limitation. Inadequate definition or deficiencies in health outcomes need to be avoided and reporting of findings could be improved in some cases. The PPR Panel proposed recommendations on how to improve the quality and reliability of pesticide epidemiology studies to overcome these limitations and to facilitate an appropriate use for risk assessment. The Panel recommended the conduct of systematic reviews and meta-analysis, where appropriate, of pesticide observational studies as useful methodology to understand the potential hazards of pesticides, exposure scenarios and methods for assessing exposure, exposure-response characterisation and risk characterisation. Finally, the PPR Panel proposed a methodological approach to integrate and weight multiple lines of evidence, including epidemiological data, for pesticide risk assessment. Biological plausibility can contribute to establishing causation.

Systematic reviews on neurodevelopmental and neurodegenerative disorders linked to pesticide exposure: Methodological features and impact on risk assessment

BACKGROUND

Epidemiological data are not currently used in the risk assessment of chemical substances in a systematic and consistent manner. However, systematic reviews (SRs) could be useful for risk assessment as they appraise and synthesize the best epidemiological knowledge available.

OBJECTIVES

To conduct a comprehensive literature search of SRs pertaining to pesticide exposure and various neurological outcomes, namely neurodevelopmental abnormalities, Parkinson's disease (PD) and Alzheimer's disease (AD), and to assess the potential contribution of SRs to the risk assessment process.

SEARCH METHODS AND SELECTION CRITERIA

Search was conducted in PubMed and Web of Science databases and articles were selected if the following inclusion criteria were met: being a SR, published until April 2015 and without language restrictions.

DATA COLLECTION AND ANALYSIS

For each neurological outcome, two review authors independently screened the search results for included studies. Data were extracted and summarized in two tables according to 16 criteria. Disagreements were resolved by discussion.

MAIN RESULTS

The total number of studies identified in the first search was 65, 304 and 108 for neurodevelopment, PD and AD, respectively. From them, 8, 10 and 2 met the defined inclusion criteria for those outcomes, respectively. Overall, results suggest that prenatal exposure to organophosphates is associated with neurodevelopmental disturbances in preschool and school children. In contrast, postnatal exposures failed to show a clear effect across cohort studies. Regarding PD, 6 SRs reported statistically significant combined effect size estimates, with OR/RR ranging between 1.28 and 1.94. As for AD, 2 out of the 8 original articles included in the SRs found significant associations, with OR of 2.39 and 4.35, although the quality of the data was rather low.

CONCLUSIONS

The critical appraisal of the SRs identified allowed for discussing the implications of SRs for risk assessment, along with the identification of gaps and limitations of current epidemiological studies that hinder their use for risk assessment. Recommendations are proposed to improve studies for this purpose. In particular, harmonized quantitative data (expressed in standardized units) would allow a better interpretation of results and would facilitate direct comparison of data across studies. Outcomes should be also harmonized for an accurate and reproducible measurement of adverse effects. Appropriate SRs and quantitative synthesis of the evidence should be performed regularly for a continuous update of the risk factors on health outcomes and to determine, if possible, dose-response curves for risk assessment.

Adsorptive Removal of Ni2+ from Aqueous Solution by Low Cost Cellulosic Adsorbent-Adsorption Kinetics and Isotherm Study

Adsorptive removal of Ni2+ from aqueous solution by low cost cellulosic adsorbent was investigated with respect to adsorption kinetics and adsorption isotherm. Adsorbent was characterized by BET surface area, SEM, EDX, FTIR and Zeta potential technique and reported earlier. The surfaces contain carbonyl and hydroxyl functional groups, which act as binding sites for Ni2+ ion. Adsorption kinetics of Ni2+ was tested by first order, Elovich, parabolic diffusion and Bangham kinetic equations. Thermodynamic parameters like ΔH ≠, ΔS ≠ and ΔG ≠ were calculated from the kinetic data. The rate of adsorption was high at high adsorption temperature. Positive values of ΔS ≠ reflect some structural exchange among the active site of the adsorbent and metal ion. Freundlich, Langmuir, Temkin isotherms and distribution coefficient were found fit to the adsorption isotherm data.

State of the art in benefit-risk analysis: food and nutrition

Benefit-risk assessment in food and nutrition is relatively new. It weighs the beneficial and adverse effects that a food (component) may have, in order to facilitate more informed management decisions regarding public health issues. It is rooted in the recognition that good food and nutrition can improve health and that some risk may be acceptable if benefit is expected to outweigh it. This paper presents an overview of current concepts and practices in benefit-risk analysis for food and nutrition. It aims to facilitate scientists and policy makers in performing, interpreting and evaluating benefit-risk assessments. Historically, the assessments of risks and benefits have been separate processes. Risk assessment is mainly addressed by toxicology, as demanded by regulation. It traditionally assumes that a maximum safe dose can be determined from experimental studies (usually in animals) and that applying appropriate uncertainty factors then defines the 'safe' intake for human populations. There is a minor role for other research traditions in risk assessment, such as epidemiology, which quantifies associations between determinants and health effects in humans. These effects can be both adverse and beneficial. Benefit assessment is newly developing in regulatory terms, but has been the subject of research for a long time within nutrition and epidemiology. The exact scope is yet to be defined. Reductions in risk can be termed benefits, but also states rising above 'the average health' are explored as benefits. In nutrition, current interest is in 'optimal' intake; from a population perspective, but also from a more individualised perspective. In current approaches to combine benefit and risk assessment, benefit assessment mirrors the traditional risk assessment paradigm of hazard identification, hazard characterization, exposure assessment and risk characterization. Benefit-risk comparison can be qualitative and quantitative. In a quantitative comparison, benefits and risks are expressed in a common currency, for which the input may be deterministic or (increasingly more) probabilistic. A tiered approach is advocated, as this allows for transparency, an early stop in the analysis and interim interaction with the decision-maker. A general problem in the disciplines underlying benefit-risk assessment is that good dose-response data, i.e. at relevant intake levels and suitable for the target population, are scarce. It is concluded that, provided it is clearly explained, benefit-risk assessment is a valuable approach to systematically show current knowledge and its gaps and to transparently provide the best possible science-based answer to complicated questions with a large potential impact on public health.

The carcinogenicity of dietary acrylamide intake: a comparative discussion of epidemiological and experimental animal research

Since 2002, it is known that the probable human carcinogen acrylamide is present in commonly consumed carbohydrate-rich foods, such as French fries and potato chips. In this review, the authors discuss the body of evidence on acrylamide carcinogenicity from both epidemiological and rodent studies, including variability, strengths and weaknesses, how both types of evidence relate, and possible reasons for discrepancies. In both rats and humans, increased incidences of various cancer types were observed. In rats, increased incidences of mammary gland, thyroid tumors and scrotal mesothelioma were observed in both studies that were performed. In humans, increased risks of ovarian and endometrial cancers, renal cell cancer, estrogen (and progesterone) receptor-positive breast cancer, and oral cavity cancer (the latter in non-smoking women) were observed. Some cancer types were found in both rats and humans, e.g., endometrial cancer (observed in one of the two rat studies), but there are also some inconsistencies. Interestingly, in humans, some indications for inverse associations were observed for lung and bladder cancers in women, and prostate and oro- and hypopharynx cancers in men. These latter observations indicate that genotoxicity may not be the only mechanism by which acrylamide causes cancer. The estimated risks based on the epidemiological studies for the sites for which a positive association was observed were considerably higher than those based on extrapolations from the rat studies. The observed pattern of increased risks in the rat and epidemiological studies and the decreased risks in the epidemiological studies suggests that acrylamide might influence hormonal systems, for which rodents may not be good models.

Nutritional epidemiology in the context of nitric oxide biology: a risk-benefit evaluation for dietary nitrite and nitrate

The discovery of the nitric oxide (NO) pathway in the 1980s represented a critical advance in understanding cardiovascular disease, and today a number of human diseases are characterized by NO insufficiency. In the interim, recent biomedical research has demonstrated that NO can be modulated by the diet independent of its enzymatic synthesis from l-arginine, e.g., the consumption of nitrite- and nitrate-rich foods such as fruits, leafy vegetables, and cured meats along with antioxidants. Regular intake of nitrate-containing food such as green leafy vegetables may ensure that blood and tissue levels of nitrite and NO pools are maintained at a level sufficient to compensate for any disturbances in endogenous NO synthesis. However, some in the public perceive that dietary sources of nitrite and nitrate are harmful, and some epidemiological studies reveal a weak association between foods that contain nitrite and nitrate, namely cured and processed meats, and cancer. This paradigm needs revisiting in the face of undisputed health benefits of nitrite- and nitrate-enriched diets. This review will address and interpret the epidemiological data and discuss the risk-benefit evaluation of dietary nitrite and nitrate in the context of nitric oxide biology. The weak and inconclusive data on the cancer risk of nitrite, nitrate and processed meats are far outweighed by the health benefits of restoring NO homeostasis via dietary nitrite and nitrate. This risk/benefit balance should be a strong consideration before there are any suggestions for new regulatory or public health guidelines for dietary nitrite and nitrate exposures.

Guidelines to evaluate human observational studies for quantitative risk assessment

BACKGROUND

Careful evaluation of the quality of human observational studies (HOS) is required to assess the suitability of HOS for quantitative risk assessment (QRA). In particular, the quality of quantitative exposure assessment is a crucial aspect of HOS to be considered for QRA.

OBJECTIVE

We aimed to develop guidelines for the evaluation of HOS for QRA and to apply these guidelines to case-control and cohort studies on the relation between exposure to benzene and acute myeloid leukemia (AML).

METHODS

We developed a three-tiered framework specific for the evaluation of HOS for QRA and used it to evaluate HOS on the relation between exposure to benzene and AML.

RESULTS

The developed framework consists of 20 evaluation criteria. A specific focus of the framework was on the quality of exposure assessment applied in HOS. Seven HOS on the relation of benzene and AML were eligible for evaluation. Of these studies, five were suitable for QRA and were ranked based on the quality of the study design, conduct, and reporting on the study.

CONCLUSION

The developed guidelines facilitate a structured evaluation that is transparent in its application and harmonizes the evaluation of HOS for QRA. With the application of the guidelines, it was possible to identify studies suitable for QRA of benzene and AML and rank these studies based on their quality. Application of the guidelines in QRA will be a valuable addition to the assessment of the weight of evidence of HOS for QRA.

On the incorporation of chemical-specific information in risk assessment

This paper describes the evolution of chemical risk assessment from its early dependence on generic default approaches to the current situation in which mechanistic and biokinetic data are routinely incorporated to support a more chemical-specific approach. Two methodologies that have played an important role in this evolution are described: mode-of-action evaluation and physiologically based biokinetic (PBBK) modelling. When used together, these techniques greatly increase the opportunity for the incorporation of biokinetic and mechanistic data in risk assessment. The resulting risk assessment approaches are more appropriately tailored to the specific chemical and are more likely to provide an accurate assessment of the potential hazards associated with human exposures. The appropriate application of PBBK models in risk assessment demands well-formulated statements about the chemical mode of action. It is this requirement for an explicit, mechanistic hypothesis that gives biologically motivated models their power, but at the same time serves as the greatest impediment to the acceptance of a chemical-specific risk assessment approach by regulators. The chief impediment to the regulatory acceptance and application of PBBK models in risk assessment is concern about uncertainties associated with their use. To some extent such concerns can be addressed by the development of generally accepted approaches for model evaluation and quantitative uncertainty analysis. In order to assure the protection of public health while limiting the economic and social consequences of over-regulation, greater dialogue between researchers and regulators is crucially needed to foster an increased use of emerging scientific information and innovative methods in chemical risk assessments.

A framework for using epidemiological data for risk assessment

Data on health effects from human exposure to chemicals provide the most direct information for risk assessment. Despite their clear relevance for risk assessment and despite the frequently made statements by regulatory bodies to use epidemiological data whenever deemed appropriate, they are not always optimally used. In this article, a framework for using epidemiological data in risk assessment is presented. Before using an epidemiologic study as the basis for risk assessment, its quality must be evaluated. The quality criteria for such a study strongly depends on the type of association between the chemical and health effect in terms of its specificity and latency period. The framework is built on the type of health effect under consideration, whether it is a specific or non-specific effect and time window of the effect, whether it is an acute, sub-acute or long-term effect. Specificity and latency are aspects that have a great impact on the choice of research design and quality criteria that must be met in order to produce reliable results appropriate for risk assessment purposes. Although expert judgement will always play an important role, the framework can help to assess if a set of epidemiological data are sufficiently reliable to serve as the basis for the derivation of health-based exposure limits. The limitations and suitability to use for risk assessment of epidemiologic studies is more likely to be the result of poor or insufficient exposure data than of poor or unreliable health effect information. It is concluded that the value of epidemiologic data not only depends on its intrinsic quality, but also on the type of health effects under consideration. In this respect, the specificity and latency play an important role.

Risk estimation for carcinogens based on epidemiological data: A structured approach, illustrated by an example on chromium

It is generally recognized that human, epidemiological data, if available, are preferred as the starting point for quantitative risk analysis above the use of data from animal studies. Although methods to obtain proper risk estimates from epidemiological data are available, several impediments prevent their widespread application. These impediments include unfamiliarity with epidemiological methods and the lack of a structured and transparent approach. We described a framework to conduct quantitative cancer risk assessment based on epidemiological studies in a structured, transparent, and reproducible manner. Important features of the process include a weight-of-the-evidence approach, estimation of the optimal exposure-risk function by fitting a regression model to the epidemiological data, estimation of uncertainty introduced by potential biases and missing information in the epidemiological studies, and calculation of excess lifetime risk through a life table to take into account competing risks. Sensitivity analyses are a useful tool to obtain insight into the impact of assumptions made and the variability of the underlying data. The framework is sufficiently flexible to allow many types of data, ranging from published, sometimes incomplete data to detailed individual data, while maintaining an optimal result, i.e., a state-of-the-art risk estimate with confidence intervals, based on all available evidence of sufficient quality.

Cassava cyanogens and fish mercury are high but safely consumed in the diet of native Amazonians

The two most important staple foods (cassava and fish) in the diet of native Amazonians contain neurotoxins (linamarin and monomethyl mercury, MMHg). These same neurotoxins are public health issues in other parts of the world. Factors such as chemistry, environment, and human ecology determine the endemism of neuropathies caused by consumption of cassava (Manihot esculenta Crantz) and fish. Linamarin is a natural component of cassava tubers that can be destroyed before consumption by proper processing. Furthermore, small amounts of the toxin absorbed by people consuming cassava can be effectively metabolized if the diet contains adequate protein-containing sulfur amino acids. Naturally occurring Hg in the waters of the Amazonian rain forest is methylated to MMHg by microorganisms and bioconcentrated in the aquatic food chain. There is no effective method for MMHg removal from fish. Despite high concentrations of naturally occurring neurotoxins in cassava (linamarin) and fish (MMHg), daily consumption of these foods in large amounts over the course of a lifetime poses no health hazards for Amazonians.

The use of consumption data to assess exposure to biotechnology-derived foods and the feasibility of identifying effects on human health through post-market monitoring

The pre-market safety assessment of foods derived through biotechnology provides a scientific basis for concluding reasonable certainty of no harm and ensuring safety. At a minimum, the outcome of such an assessment provides sufficient information to estimate the likelihood of adverse effects on consumers, generally precluding the need for post-market monitoring. Post-market monitoring (PMM) may be appropriate under certain conditions where a better estimate of dietary exposure and/or nutritional consequence of a biotechnology-derived food is required, when a potential safety issue, such as allergenicity, cannot be adequately addressed through pre-market studies, or to corroborate dietary intakes of a nutritionally improved food with beneficial effects on human health. Monitoring programs must be hypothesis-driven, and are dependent upon the availability of accurate consumption data. Exposure assessment methods include both deterministic and probabilistic estimates of intakes using food supply data, individual dietary surveys, household surveys, or total diet studies. In the development of a monitoring approach, resource allocation should be dependent upon both the desired level of conservatism and the endpoint of interest. However, the cost of monitoring varies substantially, and the potential to determine causation may be limited.

Mathematical modelling and quantitative methods

The present review reports on the mathematical methods and statistical techniques presently available for hazard characterisation. The state of the art of mathematical modelling and quantitative methods used currently for regulatory decision-making in Europe and additional potential methods for risk assessment of chemicals in food and diet are described. Existing practices of JECFA, FDA, EPA, etc., are examined for their similarities and differences. A framework is established for the development of new and improved quantitative methodologies. Areas for refinement, improvement and increase of efficiency of each method are identified in a gap analysis. Based on this critical evaluation, needs for future research are defined. It is concluded from our work that mathematical modelling of the dose-response relationship would improve the risk assessment process. An adequate characterisation of the dose-response relationship by mathematical modelling clearly requires the use of a sufficient number of dose groups to achieve a range of different response levels. This need not necessarily lead to an increase in the total number of animals in the study if an appropriate design is used. Chemical-specific data relating to the mode or mechanism of action and/or the toxicokinetics of the chemical should be used for dose-response characterisation whenever possible. It is concluded that a single method of hazard characterisation would not be suitable for all kinds of risk assessments, and that a range of different approaches is necessary so that the method used is the most appropriate for the data available and for the risk characterisation issue. Future refinements to dose-response characterisation should incorporate more clearly the extent of uncertainty and variability in the resulting output.

Hazard characterisation of chemicals in food and diet. dose response, mechanisms and extrapolation issues

Hazard characterisation of low molecular weight chemicals in food and diet generally use a no-observed-adverse-effect level (NOAEL) or a benchmark dose as the starting point. For hazards that are considered not to have thresholds for their mode of action, low-dose extrapolation and other modelling approaches may be applied. The default position is that rodents are good models for humans. However, some chemicals cause species-specific toxicity syndromes. Information on quantitative species differences is used to modify the default uncertainty factors applied to extrapolate from experimental animals to humans. A central theme for extrapolation is unravelling the mode of action for the critical effects observed. Food can be considered as an extremely complex and variable chemical mixture. Interactions among low molecular weight chemicals are expected to be rare given that the exposure levels generally are far below their NOAELs. Hazard characterisation of micronutrients must consider that adverse effects may arise from intakes that are too low (deficiency) as well as too high (toxicity). Interactions between different nutrients may complicate such hazard characterisations. The principle of substantial equivalence can be applied to guide the hazard identification and hazard characterisation of macronutrients and whole foods. Macronutrients and whole foods must be evaluated on a case-by-case basis and cannot follow a routine assessment protocol.

Hazard identification by methods of animal-based toxicology

This paper is one of several prepared under the project "Food Safety In Europe: Risk Assessment of Chemicals in Food and Diet" (FOSIE), a European Commission Concerted Action Programme, organised by the International Life Sciences Institute, Europe (ILSI). The aim of the FOSIE project is to review the current state of the science of risk assessment of chemicals in food and diet, by consideration of the four stages of risk assessment, that is, hazard identification, hazard characterisation, exposure assessment and risk characterisation. The contribution of animal-based methods in toxicology to hazard identification of chemicals in food and diet is discussed. The importance of first applying existing technical and chemical knowledge to the design of safety testing programs for food chemicals is emphasised. There is consideration of the presently available and commonly used toxicity testing approaches and methodologies, including acute and repeated dose toxicity, reproductive and developmental toxicity, neurotoxicity, genotoxicity, carcinogenicity, immunotoxicity and food allergy. They are considered from the perspective of whether they are appropriate for assessing food chemicals and whether they are adequate to detect currently known or anticipated hazards from food. Gaps in knowledge and future research needs are identified; research on these could lead to improvements in the methods of hazard identification for food chemicals. The potential impact of some emerging techniques and toxicological issues on hazard identification for food chemicals, such as new measurement techniques, the use of transgenic animals, assessment of hormone balance and the possibilities for conducting studies in which common human diseases have been modelled, is also considered.

Methods of in vitro toxicology

In vitro methods are common and widely used for screening and ranking chemicals, and have also been taken into account sporadically for risk assessment purposes in the case of food additives. However, the range of food-associated compounds amenable to in vitro toxicology is considered much broader, comprising not only natural ingredients, including those from food preparation, but also compounds formed endogenously after exposure, permissible/authorised chemicals including additives, residues, supplements, chemicals from processing and packaging and contaminants. A major promise of in vitro systems is to obtain mechanism-derived information that is considered pivotal for adequate risk assessment. This paper critically reviews the entire process of risk assessment by in vitro toxicology, encompassing ongoing and future developments, with major emphasis on cytotoxicity, cellular responses, toxicokinetics, modelling, metabolism, cancer-related endpoints, developmental toxicity, prediction of allergenicity, and finally, development and application of biomarkers. It describes in depth the use of in vitro methods in strategies for characterising and predicting hazards to the human. Major weaknesses and strengths of these assay systems are addressed, together with some key issues concerning major research priorities to improve hazard identification and characterisation of food-associated chemicals.