Web based platform for exposure assessment: Integration of databases and exposure modelling tools

1

1.Abstract

The benefit of Internet is the simplicity of distribution of data, results or any other output of research projects. The consequent disadvantage is that the quantity of available information is becoming more and more overwhelming making it increasingly laborious to find the most appropriate information. In the field of exposure and health impact assessment different kinds of databases or web-based platforms are one kind of user-friendly way to tackle this problem providing a compact way to search and combine data and tools from several sources. One of such a platform is described here. This platform provides access to databases and tools available for exposure assessment and makes it easier to find the relevant information already available for the people in the field.

2.Purpose

Evaluation of environmental health risks to humans requires assessment of the contact of humans to environmental hazards, i.e. exposures. Much exposure information and tools exist, but in disparate places. To help exposure, health risk and impact assessors, a web platform (ExpoPlatform) has been developed to provide information on various data sources and modeling tools available on the internet. This has been created as part of several projects on developing methods for integrated health risk assessment from environmental hazards. Integrated health risk assessment is the assessment of risks to human health from environmental stressors based on a whole system approach. It thus endeavours to take account of all the main factors, links, effects and impacts relating to a defined issue or problem (Briggs 2008).

The interface or "gateway" between the environment and the human body is referred to as exposure. Exposure to a hazard agent is required for there to be a possibility of a subsequent deleterious health effect. The path between the source of the hazard and the eventual effect is therefore modified by a person’s exposure. Understanding and managing exposures is therefore a key point in any assessment of interventions aimed at reducing health risks from the environment. The ExpoPlatform has been developed with the idea of providing the type of information that can be used not only in modeling both environmental concentrations and people’s contact with these concentrations.

For some chemicals and exposure situations information is widely and easily available, but for some chemicals it is not. Internet based technologies provide excellent improvements for gathering and disseminating information in the forms of electronic databases, platforms, data gateways, on-line modeling tools etc.

One advantage of this kind of technology is that it provides simple technical solutions to provide data and information freely for all users connected to internet. It also requires that persons / group of people are willing to give their products for the use of others without any financial benefits. This kind of openness and accessibility of information is beneficial because given the large amount of knowledge that has been generated, it is not well disseminated. This lack of dissemination hinders the ability of scientists, decision makers, and even the public to do effective and efficient assessments of risks. In addition internet based technologies provide means for collaborative workspaces, such as Wikipedia, which can also be utilized in the field of risk assessment as demonstrated in an open collaboration workspace called Opasnet (Opasnet www).

The purpose of this article is to describe the development and content of the Exposure Assessment Platform ( which is developed to provide free and easy access to the data and tools related to exposure assessment. At this moment the platform consists of seven different parts,and is constantly evolving to include new information.

3.Scope and Definiton

The platform development started by defining the key components needed for successful exposure assessment. The areas of interest were defined as: chemical and physiological information of chemicals, information on the sources of chemicals, concentrations of chemicals in different media (air, water, food etc.), information on the emissions of chemicals and general information on the factors effecting to the exposure levels (these include time use patterns, physiological information, consumer behavior, population size data). For these areas, the Expoplatform contains its own databases as well as links to external data, guidance, and modeling tools. The modeling tools were further defined to include tools to model/calculate the emissions, environmental fate and concentrations of chemicals in various situations, and calculating exposures. Based on this screening the data and models were divided to the following seven parts: Exposure information database (ExpoDb), Intake fraction database (iFDb), Source attribution database (SADb), Exposure modeling tool (ExpoTool), Exposure concentration database (ExpoConcDb), Exposure scenario developer (ExpoScenario) and External databases and other sources (External sources), which are described in more detailed in the following chapters.

3.1.Exposure information database (ExpoDb)

The content of this database is based on the European Commission’s priority chemical lists, which have been put up according to Council Regulation (EEC) 793/93 (Existing Substance Regulation 1993). At the moment these priority lists consists of 141 chemicals, which formulated the base for the ExpoDb. Information for these chemicals was extracted from the final and draft risk assessment reports (RARs), which are available in European Chemical Bureau’s web page (Ex-ECB).As there are no RAR’s available for all listed chemicals, some other sources of information, such as IPCS’s Environmental Health Criteria’s, have also been used. The level of information available varies between chemicals, and for some of the chemicals there was nothing available. In addition chemicals listed as priority chemicals by CDC (Centers for Disease Control and Prevention). Data was divided to 6 blocks based on the topic of information and the content of those blocks is described in Table 1.

Table 1. Content and description of the data included to the exposure information database.

Name of the block / Explanation
Chemical / Includes Einecs and CAS number, name of the chemical, information related to ECBs listing
References / Links to RAR, international chemical safety card (ICSC) and other possible sources used. Includes also links to excel files containing environmental body burden and exposure concentration information extracted from literature
Emission / Default emission factors, emission amounts and list of release media.
Properties / Chemical properties of the compound, including half-lives, solubility and partition coefficients
Sources / Information about the natural, man-made and production sources of the compound. In addition information about production volumes and use of the compound.
Exposure / Reference to the pages of RAR’s where information about the exposure can be found. In addition predicted environmental concentrations in regional and continental level for air, water and soil.

Purpose of ExpoDb is to provide chemical related information, which is needed for exposure assessment especially in situations when the exposure concentrations are modeled with fate and dispersion models. Information in the database can be search based on the chemical name and CAS or EINECS number.

3.2.Intake fraction database (iFDb)

Information to the intake fraction database was extracted from the published intake fraction articles. Data related to the study scenario with the obtained results was divided to several blocks, which are described in more detailed in Table 2. Information was categorized by individual chemical or exposure substance, such as particle or compound, providing a possibility to make searches based on the substance.

Table 2. Structure of the intake fraction database.

Name of the block / Explanation
Type of study objective / agent / Possible choices are: chemical, particle or particle precursor
Specification of study objective / More informative specification of study object such as name of the chemical, particle size/type, chemical group
Geographical location / Which country and city
Target population / Possible choices are: one individual, one individual in certain microenvironment, individuals in certain microenvironment, individuals in certain activity or whole population of the target area
Population characteristics / More informative description of target population such as child, adults, some subgroup, urban, rural
Population size / Number of exposed people or number of exposed people/km2
Region level / Possible choices are: local, county, national, regional, continental or global
Region size / Area (km2) or distance from the source
Source / Possible source group are: traffic, power plants, all sources, indoor sources, industry, general sources to air or environmental tobacco smoke (ETS)
Definition of source / More informative description of source such as type of industrial plant, what indoor source, what vehicle
Number of source sites / Number of source sites such as number of plants
Source type / Possible choices are: point, line, mobile, diffuse, area
Source height / Source height as meters, or used mixing height
Emission amount / Amount of emission used in calculations as ton/year (very limited availability)
Medium / Possible choices are: air, water, soil or multimedia
Definition of medium / More informative description of release media such as indoor air, outdoor air, waste water, river water, natural soil, what mediums in multimedia etc.
Exposure pathway / Possible choices are: inhalation, ingestion, dermal
Time scale / Season / Time scale or season used in calculations such as lifetime, year, 24 hours, summer, winter
iF / Calculated intake fraction value, if results are provided as one value
iF type / Type of calculated intake fraction value such as average, mean, median
iF range / Possible range of calculated intake fraction values, which can be between sites, between locations
Method / Used method such as CALPUFF, empirical, statistical methods, CalTOX, EUSES, Gaussian plume modeling, Monte Carlo
Used approximations etc. / More informative descriptions of the modeling parameters such as used values
Reference of the data / Reference of the data source

Content of iFDb can be utilized for several purposes. One way is just to use it as a reference library to the studies using intake fraction as a method. The results provided in the database can be used to compare previous results with the result obtained in the users own studies. Study results can also be analyzed further to be used to screen the levels of exposure in various situations and to make rough estimations of exposure levels for similar situations.

3.3.Source attribution database (SADb)

This database compiles results of previous SA studies and is this way similar to iFDb. For practical reasons it was necessary to make some selections criteria for publications inserted to this database, because the number of articles with source attribution results is so huge. The main criterion was the way that the results were presented, so that those were similar enough to allow formation of the result tables. Content of SADb is structured as presented in Table 3.

Table 3. Content of source attribution database

Study specifications
Content of the block / Explanation
Compound / Name of the target compound such as coarse particles, PM, VOC, non-methane hydrocarbons
Geographical location / Country and town of the study
Region level and type / Region level such as local, regional, and region type such as urban, industrialized, ambient
Measurement period / Time of the measurement period as month and year
Time resolution for data / Time resolution of data such as 24 hours, 3 hours
Medium / Medium such as air, soil, water
Chemical elements / List of analyzed chemical elements or number of them
Method / Name of the used method such as PCA, CMB, PMF
Source profile / Used source profile such as based on literature, SPECIATE database
Study reference / Reference of the study
Results
Content of the block / Explanation
Source attribution results / Results of the source attribution as % or concentration with source terms and used tracers
Measured concentrations / Results of the measured concentrations as exposure concentration and/or as amount of chemical species analyzed

SADb is structured similarly with intake fraction database, so it can also be used as a reference library. Data in there can also be analyzed further to provide summaries on what kind of source attribution methods have been used in which situations and also to provide information of the usual sources in variety of environments.

3.4.Exposure modeling tool (ExpoTool)

This tool provides a means to calculate four exposure-related outcomes: a) concentration, b) exposure, c) intake and d) intake fraction. These outcomes are calculated using a simple non-steady state box model that incorporates first-order reaction rates (exponential decay). The tool will provide a deterministic (i.e. one number) output, meant to give the user an order-of-magnitude idea of the result that can be useful for issue-framing and screening-level priorization.

As tool exists now, it allows for a simple first order calculation. Users can run it several times to get a range of results. It is useful for screening situations where the user would like to get an idea of the potential exposures for a particular situation.

3.5.Exposure concentration database (ConcDb)

The purpose of this database is to provide measured exposure concentrations representing the population of some larger target area. Measured data for personal exposure with measured microenvironmental, such as home outdoor, home indoor and work place, and media concentrations are gathered from published studies. Results are presented usually with statistical measures like mean, median, SD and percentiles when available. In addition for EXPOLIS study the results of individual samples are provided. ConcDb is structured as presented in Table 4.

Table 4. Content of Exposure concentration database

Content of the block / Explanation
Compound / Name of the target compound
Concentration type / Type of the concentration environment or medium. Possibilities are: home indoor, home outdoor, personal, work, drinking water, indoor dust, human, soil, beverage, food, in-vehicle, school
Data description / Description of the result i.e. title of the table
Study description / Description of the study
Study reference / Reference of the study
Additional info / Some additional info for the result when needed

The ConcDb can be utilized to provide distributions of exposures in several locations for risk assessment purposes and it can also be used to predict exposures in locations where no measured information is available. This database is also the place where the measured values can be easily distributed for others to allow them to be used widely as possible.

3.6.Exposure scenario developer

The International Programme on Chemical Safety (IPCS) defines an exposure scenario as:

A set of conditions or assumptions about sources, exposure pathways, amounts or concentrations of agent(s)involved, and exposed organism, system, or (sub)population (i.e., numbers, characteristics, habits) used to aid in the evaluation and quantification of exposure(s) in a given situation (IPCS 2004).

This definition refers to "agents" defined as "a chemical, biological, or physical entity that contacts a target" (IPCS 2004) and may cause a health hazard. The simplest way to think of an exposure scenario is as the description of how an individual or population comes into contact with an agent.

For integrated environmental health assessments, the exposure scenario needs to incorporate both upstream linkages (sources, activities, behaviours) that influence exposure and the downstream linkages (exposure-response functions, health outcomes) that depend on exposures. The purpose of this part of the platform is to give guidance on how to scope and define exposure scenarios. Usually this step is the start of the whole modeling process and it defines the data and modeling tool needs specifically for each individual study. Guidance is in the form of questions that should be asked and answered when scoping the issue and defining the scenarios. In addition there is schematic presentation of a causal diagram, which provides a simple and clear way of describing the causality of individual objects of the assessment covering also other aspects of the assessment chain than just the exposure part. There is a downloadable file provided for the causal diagram to be used as a starting point for a new assessment.

3.7.External databases and other sources (External sources)

In this part of the platform other freely available exposure assessment related databases, tools and guidance documents were collected together. Information is divided further inside the three main categories as presented in Table 5.

Table 5. Categories of databases and tools in external sources

Main category / Sub-categories
Databases / General exposure factors: Time activity data, Ingestion data, Consumption data for pesticides, Physiological data, Housing data, Mobility data for people, Land use data, Population data
Media concentrations: Indoor air, Outdoor air, Water (river, lake, drinking water), Soil and sediment, Food (including breast milk), Biomonitoring data, Consumer products
Emissions: Air, Water, Soil and sediment, Emission profiles, Emission factors
Chemical properties: General properties, Fate properties, Toxicological properties
Occupational exposure: Occupational exposure limits
Tools / Concentration: Outdoor air, Indoor air, Water, Soil and sediment, Multimedia, Food (including breast milk)
Exposure: Inhalation, Ingestion, UV-radiation, Dermal, Multipathway, Multimedia, Source attribution, General assessment
Chemical properties: Chemical properties
Emission models: Vehicles, Radiation
GIS: Mapping
Guidance documents / Exposure assessment: General exposure assessment, Source attribution, Consumer products, Dermal exposure, Interspecies extrapolation

All information is tagged with keywords and this provides a possibility to search information based on a word. New information is linked as found and needed, and new categories can be added easily.

This part of the platform functions as an information library to collect all relevant data available in Internet. This way the user does not need to Google information time after time, because it can be found easily through Expoplatform. There are also short descriptions of linked databases and tools provided, so that user could evaluate the usefulness of the linked information without the need to go through the original source.