multi_tox {stressaddition}

Predict the survival of binary toxicant mixtures

Description

The Multi-TOX model predicts the effects of binary toxicant mixtures based on three-phasic concentration-response relationships. See the publication for details.

Usage

multi_tox(
  model_a,
  model_b,
  concentration_a,
  concentration_b,
  sa_contribution = 0.5,
  survival_max = 100
)

Arguments

model_a, model_b

The ecxsys models of the toxicants.

concentration_a, concentration_b

The concentrations of the toxicants in the mixture. Both vectors must either be the same length or the longer length must be a multiple of the shorter length. That's because the shorter concentration vector gets recycled to the length of the longer one.

sa_contribution

The proportion of stress addition contributing to the calculation of the toxicant stress in the mixture. Must be between 0 and 1 where 1 stands for 100 % stress addition.

survival_max

Controls the scaling of the result. This represents the maximum value the survival could possibly reach. For survival data in percent this should be 100 (the default).

Details

The predictions are symmetric, i.e. it does not matter which of the toxicant models is a or b as long as the concentration arguments are supplied in the same order.

This method is only suitable for experiments without or with low environmental stress. Any environmental stress supplied as arguments to ecxsys in model_a or model_b is ignored.

Value

A data frame with columns of the supplied concentrations and the corresponding mixture survival and stresses.

References

Liess, M., Henz, S. & Shahid, N. Modeling the synergistic effects of toxicant mixtures. Environ Sci Eur 32, 119 (2020).

Examples

# Using a data set which is included in this package. See ?multiple_stress
ms <- multiple_stress
esfen <- ms[ms$food == 1 & ms$prochloraz == 0, ]
proch <- ms[ms$food == 1 & ms$esfenvalerate == 0, ]

model_esfen <- ecxsys(
    concentration = esfen$esfenvalerate,
    survival_tox_observed = esfen$survival,
    hormesis_concentration = 0.1
)
model_proch <- ecxsys(
    concentration = proch$prochloraz,
    survival_tox_observed = proch$survival,
    hormesis_concentration = 100
)

# Predict the survival at 8 different esfenvalerate concentrations
# but keep the prochloraz concentration constant at 32:
mt <- multi_tox(
    model_esfen,
    model_proch,
    c(0, 0.0001, 0.001, 0.01, 0.1, 0.316, 1, 3.16),
    32,
    sa_contribution = 0.8
)
mt[1:3]  # The concentrations and survival of the 8 mixtures.

# Predict the survival at 4 different combinations
# of esfenvalerate and prochloraz:
mt <- multi_tox(
    model_esfen,
    model_proch,
    c(0.1, 0.2, 0.3, 0.4),
    c(0, 1, 32, 100),
    sa_contribution = 0.8
)
mt[1:3]  # The concentrations and survival of the 4 mixtures.