dir.inhal.aer: dir.inhal.aer

In HumanExposure/SHEDSDevel: The SHEDS-HT model for estimating human exposure to chemicals.

Description

Models the inhalation exposure from the use of aerosol products for each theoretical person.

Usage

dir.inhal.aer(sd, cd, cb, io)

Arguments

sd	The chemical-scenario data specific to relevant combinations of chemical and scenario. Generated internally.
cd	The list of scenario-specific information for the chemicals being evaluated. Generated internally.
cb	A copy of the base data set output from the make.cbase function, with columns added for exposure variables.
io	A binary variable indicating whether the volume of the aerosol is used to approximate the affected volume.

Details

This scenario considers inhalation exposure from the use of aerosol products. Typical examples include hairspray and spray-on mosquito repellent. The function produces a prevalence value, which reflects the fraction of the population who use this scenario at all. It also produces a frequency value, which is the mean number of times per year this scenario occurs among that fraction of the population specified by prevalence. Since SHEDS operates on the basis of one random day, the frequency is divided by 365 and then passed to the p.round (probabilistic rounding) function, which rounds either up or down to the nearest integer. Very common events may happen more than once in a day. The function also produces a mass variable, which refers to the mass of the product in grams in a typical usage event. The composition is the percentage of that mass that is the chemical in question. frac.aer is the fraction of the product mass that becomes aerosolized, and the volume affected by the use is approximated to allow the calculation of a concentration or density. Defaults are set in the code if these variables are missing from the input file. Exposure for the inhalation pathway has units of micrograms per cubic meter, reflecting the average air concentration of the chemical. An airconc variable is defined using mass, composition, frac.aer, and volume. Since exposure depends on the time-averaged concentration, a duration is necessary. For example, if one spends five minutes in an aerosol cloud and the rest of the day in clean air, the daily exposure is the cloud concentration multiplied by 5/1440 (where 1440 is the number of minutes in a day). This function also calculates the inhaled dose, in units of micrograms per day. The dose equals the product of exposure (g/m3), basal ventilation rate, bvr (m3/day), the METS factor of 1.75 (typically people inhale air at an average of 1.75 times the basal rate to support common daily activities), and a conversion factor of 1E+06 from grams to micrograms.

Value

dir.inh.aer The calculated quantity of chemical inhalation from aerosols, like hairspray and similar products, that are directly injected into the air on or around each exposed person.

Author(s)

Kristin Isaacs, Graham Glen

keyword ~SHEDS

HumanExposure/SHEDSDevel documentation built on Oct. 30, 2019, 6:49 p.m.