End-to-end pollution burden

Chains the concentration-response function, the attributable fraction and the baseline case count into annual attributable cases, as the GBD risk factor estimates do (GBD 2019 Risk Factors Collaborators 2020). Use it for a single population (a city, a region) when you know its mean exposure, its baseline rate and its size; for many areas at once see polbrdarea.

Usage

polbrdn(
  expomean,
  expoprev,
  brate,
  pop,
  poll = "NO2",
  y = "allcause",
  refconc = NULL,
  rare = FALSE,
  hirate = FALSE
)

Arguments

expomean

The mean exposure among the exposed, in micrograms per cubic metre. With expoprev = 1 that is the population mean.

expoprev

Proportion of the population at that level (1 for ambient air), in [0, 1].

brate

Cases per person-year in the unexposed scenario (a rate per person, not per 100,000: 0.008 is 800 per 100,000).

pop

At-risk population (persons; any non-negative number).

poll

"PM2.5" (also written "PM25") or "NO2", in either case.

y

Outcome key passed to the concentration-response function; extra$unit says whether the attributable count is deaths or incident cases.

refconc

Counterfactual concentration; NULL takes the pollutant's default (PM2.5 5.8, NO2 10; see crfpm25).

rare, hirate

TRUE to admit a baseline rate below 1e-5 (one per 100,000) or above 0.1 (10,000 per 100,000) per person-year, as vrfpol does: without them such a rate is refused, being also what a rate in the wrong unit looks like.

Value

A list of class rmbl_burden (plot() draws it) with: paf (the attributable fraction), attrcases and basecases (per year), population, brate (per person-year), expomean, refconc (the one used), pollutant ("PM2.5" or "NO2"), citation (a string), and extra, a list with rr, logrr, outcome and unit ("deaths" or "incident cases").

Details

The steps are: the relative risk at expomean from crfpm25 or crfno2 (with the reference concentration given or the pollutant's default); the attributable fraction from attrfrac with expoprev; the baseline cases \(y_0 N\); and the attributable cases, their product. The result is a yearly count of deaths (or incident cases for "chiast").

Refusals: an unknown pollutant, an outcome the pollutant's CRF does not have, any input that is not a single finite non-negative number, and a baseline rate outside the band described in mortdisp unless rare or hirate admits it.

References

GBD 2019 Risk Factors Collaborators (2020). Global burden of 87 risk factors in 204 countries and territories, 1990-2019. The Lancet 396(10258), 1223-1249.

Examples

# Ambient NO2 of 25 micrograms per cubic metre over a million people.
b <- polbrdn(25, 1, 0.008, 1e6, poll = "NO2")
b$attrcases
#> [1] 234.1369
b$paf
#> [1] 0.02926711

# PM2.5 and ischaemic heart disease deaths, against the WHO guideline
# of 5 as the counterfactual.
polbrdn(12, 1, 0.0012, 2.8e6, poll = "PM2.5", y = "ihd",
                 refconc = 5)$attrcases
#> [1] 1235.817

# Childhood asthma counts incident cases, not deaths.
polbrdn(30, 1, 0.012, 5e5, y = "chiast")$extra$unit
#> [1] "incident cases"

# Only PM2.5 and NO2 have concentration-response functions here.
try(polbrdn(40, 1, 0.008, 1e6, poll = "O3"))
#> Error : Unknown pollutant 'O3'. Use 'PM2.5' or 'NO2'.