Risk assessment activity patterns

The Modeling Engine in THERdbASE has the following model groups 1) Population Distributions, 2) Location/Activity Patterns, 3) Food Consumption Patterns, 4) Agent Releases Characteristics, 5) Microenvironment Agent Concentrations, 6) Macroenvironment Agent Concentrations, 7) Exposure Patterns and Scenarios, 8) Dose Patterns, and 9) Risk Assessment. 

Accurate exposure and biological monitoring data are crucial to the evaluation of residential exposure and risk estimates since the potential health risks associated with a pesticide depend on the amount of exposure to the pesticide, its toxicity and the susceptibility of the exposed population. Prediction of whether adverse health effects will occur in humans can be made by comparing the exposure estimate to the No Observed Adverse Effect Level (NOAEL) derived from the animal toxicity data. Uncertainty arises from the input data used in an assessment, e.g. variability in time-activity patterns, contact with exposure media, bioavailability, exposure duration, frequency of product use and differences in the route of exposure in humans from that in the animal studies (since absorption, distribution, metabolism and elimination kinetics may differ substantially by exposure route). 

THERdbASE contains two major modules, namely a Database Module and a Model Base Module. The Database Module relates information from exposure, dose and risk-related data files, and contains information about the following population distributions, location/activity patterns, food-consumption patterns, agent properties, agent sources (use patterns), environmental agent concentrations, food contamination, physiological parameters, risk parameters and miscellaneous data files. The Model Base Module provides access to exposure dose and risk-related models. The specific models included with the software are as follows Model 101, subsetting activity pattern data Model 102, location patterns (simulated) Model 103, source (time application) Model 104, source (instantaneous application) Model 105, indoor air (two zones) Model 106, indoor air (n zones) Model 107, inhalation exposure (BEAM) Model 108, inhalation exposure (multiple chemicals) Model 109, dermal dose (film thickness) Model 110, dose scenario (inhalation/dermal) Model 201, soil exposure (dose assessment). 

There is an emerging body of evidence that suggests person-to-person differences in exposure play an important role in the variability and uncertainty associated with risk assessments for chemicals (and other agents). The traditional or standard default approaches used in human health risk assessment often do not effectively evaluate interindividual variation and may underestimate the impact of chemical exposures on particular groups of individuals. Traditional approaches must be refined to adequately account for temporal variation in factors that contribute to complex aggregate exposure patterns (e.g., chemical-specific exposure media concentrations and time-activity interactions by humans) involving multiple, intermittent exposures. 

The exposure characteristics and assumptions refer partly to site conditions e.g. soil type, soil chemistry, exposed soil fraction) and partly to the site use and users e.g- construction style of buildings, receptor characteristics, activity patterns and time spent on site). Many of these are assumptions rather than measurements because chronic health risk assessments are concerned with predicting contaminant intakes and their effects up to 70 years into the future. Some of the soil characteristics may also change with time. 

A risk assessment requires a characterization of exposure setting. In this step, the assessor characterizes the exposure setting with respect to the general physical characteristics of the site and the characteristics of the populations on and near the site. Basic site characteristics such as climate, vegetation, ground-water hydrology, and the presence and location of surface water are identified in this step. Populations are also identified and are described with respect to those characteristics that influence exposure, such as location relative to the site, activity patterns, and the presence of sensitive subpopulations. The characteristics of the current population, as well as those of any potential future populations are considered. 

The subject of this particular volume relates to aerosol particle physics including aerosol characterisation, the formation mechanism, the aerodynamic size distribution of the activity and aerosol residence time, instrumentation techniques, aerosol collection and sampling, various kinds of environmental (atmospheric aerosols), particularly radioactive aerosols and the special case of radon decay product aerosols (indoors and outdoors) and the unattached fl ac-tion, thoron decay product aerosols, the deposition patterns of aerosol particles in the lung and the subsequent uptake into human subjects and risk assessment. 

The fact that dioxin-like compounds are ubiquitous in the environment may have further implications for low-dose risk assessment. Special populations may receive identifiable, incremental exposures, based on proximity to specific sources or specific human activity patterns. 

The risk assoeiated with the inhalation of particulate PAHs indoors showed that the contribution of BaP to the total carcinogenic potential was dominant in the range of 51% to 64%. Human activity patterns indicate that people tend to spend 90% or more their time indoors. In addition, indoor BaP ooncentrations are strongly afifeeted by the corresponding outdoor ones. Thus, the risk assessment for inhalation of PAH could be roughly estimated by only the outdoor BaP eoneentrations. 

---