stressaddition

This is the R implementation of the tri-phasic concentration-response model introduced in Liess, M., Henz, S. & Knillmann, S. Predicting low-concentration effects of pesticides. Sci Rep 9, 15248 (2019). It allows modeling of ecotoxicological experiments where the response shows signs of a hormesis effect.

Installation

Stressaddition is not on CRAN. You can install the most recent stable version from GitLab using the devtools package:

# install.packages("devtools")
devtools::install_gitlab("oekotox/stressaddition", host = "git.ufz.de")

Alternatively there are binary and source builds downloadable from the releases page.

Updating

RStudio's integrated package updater won't detect updates in packages installed from GitHub or GitLab. I recommend running

devtools::update_packages()

in regular intervals to check for updates from those sources.

Citation

Please cite this package if you use it in your analysis. See citation("stressaddition") for details.

Example

In the paper we use the model in the context of survival experiments. However, it can also be applicable in modeling other concentration or dose dependent responses. For this reason the more general term "effect" instead of "survival" is used throughout the package.

library(stressaddition)
model <- ecxsys(
    concentration = c(0, 0.03, 0.3, 3, 10),
    hormesis_concentration = 0.3,
    effect_tox_observed = c(85, 76, 94, 35, 0),
    effect_tox_env_observed = c(24, 23, 32, 0, 0)
)

# Plot the effect and the system stress:
par(mfrow = c(2, 1))
plot_effect(model)
plot_stress(model)

# The LC50 of the effect under the influence of toxicant and system tress:
ec(model, "effect_tox_sys", 50)

# The LC10 of the effect under the influence  of toxicant, system and environmental tress:
ec(model, "effect_tox_env_sys", 10)