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Biomedical subjects

M A Jayjock

Publications and source records attributed to M A Jayjock.

15 recordsLinked to original sources
PubMed2002

Implications of hormesis for industrial hygiene.

This paper considers hormesis as a valid and potentially valuable alternative hypothesis for low-dose response in the context of occupational health risk assessment. It outlines the current occupational risk assessment paradigm and its use of high-dose toxicological data in setting occupational exposure limits (OELs). This present effort is a call to science to investigate the potential promise of hormesis in providing prima facie experimental evidence for a low-dose threshold of toxic effect to chemical agents. The scientific effort and advancement advised in this piece could also lead to experimentally validated quantitative estimates of the toxic effect extant at occupational exposures in the region of the OEL.

Animals↗
PubMed2002

Jayjock and Lewis reply.

The current state-of-the-science, in our opinion, is incapable of accurately predicting the human health risk at environmental exposures to chemicals. We believe that dose-response models represent an integral part of the scientific method but that all models require valid scientific data in the realm of actual exposure in order to be derived and function properly. Given this current state, the evidence to date and the promise of hormesis to provide a detectable signal at low-dose, we view it as a variable and valuable hypothesis worthy of significant scientific effort.

Animals↗
PubMed1998

Risk assessment of contact allergens.

BACKGROUND: Quantitative risk assessment has been used successfully for a number of human health hazards associated with product use. Dermal contact allergy or sensitization is a relatively late addition to the list. OBJECTIVE: This article outlines the concepts and operational elements of product safety risk assessment of contact allergens. METHODS: The basic risk assessment paradigm is presented along with various dermal dose metrics in the context of their application in describing the dose response or risk of allergic response per unit dose of a product. This analysis of toxic effect is then combined with an assessment of exposure in the real world to estimate the risk of elicitation of active skin disease. RESULTS: Human health risk assessment in general and as it is applied to contact allergy in particular is an emerging science. As with any real science, it allows for the formulation and testing of hypotheses that elucidate a model or description of reality. The model, in turn, allows for predictions that, in this case, are the risk assessments. Of course, the elements of this model and its predictions are also then testable in successive rounds of hypothesis formation and investigation. The entire system runs on data, and a lack of data with a concomitant abundance of scientific uncertainty limits the utility and ultimately the credibility of the process. CONCLUSIONS: Uncertainty from variability and lack of knowledge notwithstanding, the risk assessment paradigm and its scientific construct are valuable in gauging and ultimately controlling the risk of contact allergy from products.

Algorithms↗
PubMed1997

Monte Carlo uncertainty analysis of a diffusion model for the assessment of halogen gas exposure during dosing of brominators.

Monte Carlo simulation was incorporated into a diffusion-based exposure assessment model for the estimation of worker exposure to halogen gases during dosing of 500-lb sacks of a bromine-based biocide (BCDMH) into brominators. Indoor and outdoor dosing scenarios were modeled for small and large brominators. The diffusion model used describes a concentration gradient of halogen as a function of distance and time from the source instead of ascribing worst-case single point value estimates to the variables used in the diffusion model. Monte Carlo simulation was used to describe a distribution of values for each appropriate model variable. Using a personal computer and Monte Carlo simulation software, 10,000 iterations of the diffusion model were performed for four different dosing scenarios using random and independent samples from the distributions entered. The corresponding output distributions of predicted exposures were then calculated and displayed graphically for each scenario. The results of the Monte Carlo simulation predict that outdoor dosing of either small or large brominators with BCDMH is highly unlikely to result in an exceedance of the working occupational exposure limit for total halogen. In most ambient wind speed conditions, diffusion prevents appreciable airborne exposure to workers in the immediate vicinity of the brominator. Although relatively uncommon, dosing of brominators indoors in the assumed absence of local exhaust ventilation may generate airborne concentrations of total halogen that exceed the working short-term occupational exposure limit. Although very limited and inconclusive, field trial monitoring of BCDMH transfer operations indoors resulted in halogen concentrations well within the distribution of concentrations predicted by the Monte Carlo simulation of the diffusion model.

Air Pollution↗
PubMed1996

Product safety, risk assessment, and responsible care in the biocide chemical industry.

Manufacturers of biocides recognize a need to control the risk from their products. This paper discusses some of the history and critical aspects of these activities and outlines the needs under the current initiatives of Responsible Care. Biocide product safety risk assessment is operationally defined in this context and presented as the fundamental tool of the process. The need for data and the criteria for its dissemination are discussed along with the requirement that the data-gathering effort be combined in joint efforts with scientists in industry, academia, and the regulatory community.

Biological Availability↗
PubMed1996

Formulation effect on the dermal bioavailability of isothiazolone biocide.

A central tenet of the science of toxicology is that the toxic effect of any material monotonically increases with the amount of the material delivered to the target tissue. This is the so-called dose-response relationship. Previous work is discussed in which a dose-response relationship is established for the induction and elicitation of cutaneous contact allergy from the isothiazolone biocide which is a 3 to 1 mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one. The commercial product name for this mixture is Kathon LX biocide. Given a tissue dose-response, this current work determines and demonstrates a difference in risk from aqueous formulations with and without polymer. A lower delivered dose of biocide goes into the skin from an aqueous-based polymeric emulsion or paint than from an aqueous solution or oil-in-water emulsions without polymer. Thus, the estimate of risk, as a direct result of dose, and the determination of a safe use level of a biocide in any particular formulation matrix need to incorporate this reality.

Animals↗
PubMed1993

A proposal for improving the role of exposure modeling in risk assessment.

This paper explores the adequacy of using currently available exposure assessment models for indoor air inhalation exposures in the context of the uncertainty that exists in both the dose-response assessment and the exposure assessment. A tiered system is proposed for implementing exposure assessments. Each tier involves additional research, but also would lead to reductions in uncertainty. The authors discuss a possible comprehensive research program that will permit the building of well-validated models for indoor air inhalation exposures among classes of chemicals, building types, and exposure scenarios. The authors believe that until such a research program is undertaken, modeling of exposures (and therefore risks) using the current, unvalidated modeling approaches provides little more than worst-case estimates that are useful primarily for making screening decisions about risks.

Air Pollution, Indoor↗
PubMed1993

Quality requirements for biocides in the 1990s.

Increasing regulatory and product safety standards along with the enhanced expectations of today's consumer public have dramatically changed the manner in which new biocides are researched, developed, and marketed. Potential candidates face ever rising quality hurdles regarding Product Efficacy, Toxicology, Human Health and Environmental Risk Assessment and Risk Management, and, ultimately, Product Stewardship. These pressures have resulted in long lead times for new products with few companies entering into the biocide market. Another resultant trend has been a strong tendency to expand the life cycles of existing products. This report outlines and summarizes recent activity associated with these quality issues and their relationship to the successful marketing of biocides in the future.

Chemical Industry↗
PubMed1992

A rationale and framework for establishing the quality of human exposure assessments.

Exposure assessments, performed as input to an evaluation of potential human health risk, are an element of risk assessment. Risk assessment results feed governmental and corporate risk management decisions, which seek to balance the estimated potential human health risks with other factors. Risk managers presume that the risk information provided to them is scientifically valid and accurate. Government agencies have begun to apply a system known as good laboratory practices (GLP) to ensure adequate data quality on animal studies, which are often the first step in the health-effects evaluation of risk assessment. This paper explores a rationale and framework for establishing the quality of human exposure assessments and proposes a set of good exposure assessment practices (GEAP). The components of the proposed GEAP include the writing of a study protocol before conducting the study, consideration of available resources, specification of an exposure model, a study design (including sampling and analytical methods and data analysis), quality assurance, archiving, communications, and a statement of overall uncertainty in exposure estimates. The GEAP concept is offered as a starting point for developing a consensus among the community of exposure assessors regarding a minimum standard for good practices. If a consensus on GEAP can be reached and applied, exposure assessments would have improved scientific bases, interpretability, and utility.

Environmental Monitoring↗
PubMed1992

A quality process for chemical product risk assessment.

One cannot manage a health or environmental risk of unknown dimension. Thus, the rational and cost-effective control of any risk lies first in its reasoned assessment. The assessment of risk is a scientific endeavor which embodies the intellectual use of information to reach a determination or assignment of an ascribed level of danger. It is, however, a decision process and approach whose details are substantially value laden. As such, it is potentially subject to a myriad of subjective interpretations from individuals with special interests and perspectives. Given this nature, it is incumbent upon those responsible for risk assessment in any organization to formulate a broad-based scientific consensus regarding the principals of quality assurance for the risk assessment process in their organization. This paper attempts to outline a rational and prudent consensus-based system for the quality assurance of risk assessment concerned with the danger to human health and the environment posed by the use of chemical products. We present it as a model that we hope could be accepted and implemented.

Chemical Industry↗
PubMed1991

Regulating the introduction of new chemicals under section 5 of TSCA: improving the efficiency of the process and reducing potential injury in the workplace through the use of operational MSDS and exposure limits.

The Toxic Substances Control Act (TSCA) authorizes the EPA to take appropriate actions to ensure that new and existing chemicals do not pose "unreasonable risk" to health or the environment. Section 2(b)(3) of the Act directs the Agency to accomplish this objective in a manner that does "not impede unduly or create unnecessary economic barriers to technological innovation." In recent years, critics have felt that the EPA has failed to achieve these primary goals of TSCA. This paper considers some of the reasons for this criticism and advocates an alternate approach of exposure limits and operationally sufficient controls to assist in achieving these goals. An illustration of how this alternate approach might work under practical conditions is presented, using as an example a new chemical substance from the class of acrylate monomers. These concepts and risk assessments provide data for a better design of future studies according to good laboratory practice and quality assurance.

Chemical Industry↗
PubMed1988

Assessment of inhalation exposure potential from vapors in the workplace.

Quantitative knowledge of human exposure to a chemical represents half of the required input for the health risk assessment process by which occupational health professionals seek to integrate exposure and inherent hazard in clinically meaningful terms. This work reviews and presents explicit methodologies and approaches to the estimation of inhalation exposure to chemicals. Special attention is given to estimating vapor exposures and the critical elements of an indoor air pollution model that assumes conservation of contaminant mass in a specified box of workroom air.

Air Pollutants↗
PubMedDate not supplied

How protective are respirator assigned protection factors: an uncertainty analysis.

This investigation evaluated the risk of overexposure for a selected assigned protection factor by performing Monte Carlo simulations. A model was constructed to assess respirator performance by calculating the concentration inside the respirator. Estimates of the factors that affect respirator performance were described as distributions. The distributions used a worst case estimate for concentration in the workplace, the worst case for respirator performance (the fifth percentile person), and the worst case for exhalation valve leakage. A Monte Carlo analysis then provided estimates of the percentage of time that concentration inside the respirator exceeded the occupational exposure limit (OEL). For a half-facepiece respirator with an APF of 10, the calculations indicated a low risk of being exposed above an OEL, with mean exposures being controlled well below an OEL.

Humans↗
PubMedDate not supplied

Quantitative level of protection offered to workers by ACGIH threshold limit values occupational exposure limits.

The details of the example or modeling methodologies used herein are not critical to the general point of this article, which advises the estimation of residual risk at the OEL by using some quantitative modeling structure. Specifically, the authors believe that an explicit attempt to gauge the level of residual risk at the OEL based on conceptual stochastic models with transparent and testable assumptions could be seen as an important enhancement to the process. This is especially true in sharing the OEL deliberations and explaining OEL decisions to the stakeholders. Indeed, if this approach is used, it is critically important to understand and continually communicate that this "cloud of uncertainty" represents model estimates in which the true risk would most likely be less than worst case estimates and could possibly be zero. It is also possible but highly unlikely that it could be higher than the worst case upper-bound estimate. The above quantitative estimation scheme represents a possible improvement that could provide a reasoned attempt on the part of the risk assessors to use rational science (i.e., conceptual models with transparent and testable assumptions) to inform all of the OEL users and stakeholders of their meaning.

Air Pollutants, Occupational↗