Short-term effects of air pollution and temperature on cattle mortality in the Netherlands

Background: Extreme temperatures and air pollution are both associated with increased mortality risk in humans. However, the effects of temperature and air pollution on cattle have not been investigated much before.

Objectives: Short-term effects of temperature (heat and cold) and air pollution on cattle mortality were investigated and quantified in the Netherlands during 2012–2017.

Methods: Daily data on cattle mortality, weather conditions and mean levels of particulate matter (PM₁₀), ozone (O₃), ammonia (NH₃) and nitrogen dioxide (NO₂) of the Netherlands during 2012–2017 were collected. Associations were investigated with time–series regression using distributed lag non–linear models including lags of up to 25 days. Effects of temperature were expressed as those associated with extreme and moderate heat or cold, defined as Temperature Humidity Index (THI) values below the 1st and 5th percentile, and above the 95th and 99th percentile of the national THI distribution. Effects of air pollutants were expressed per 10 μg/m³ change in daily mean concentrations.

Results: Both high and low temperatures were associated with increased mortality amongst different age groups. For instance, the newborn calves of at most 14 days showed a cumulative relative risk (RR) of 2.13 (95%CI: 1.99–2.28) for extreme heat and the pre-weaned calves (15–55 days) showed a cumulative RR of 1.50 (95%CI: 1.37–1.64) for extreme cold. Associations of air pollution with mortality were not consistent, except for the effect of ozone of lag 0–7 and lag 0–25. Exposure to O₃ in the newborn calves resulted in a cumulative RR of 1.09 (95%CI: 1.04–1.4) for lag 0–7 and 1.09 (95%CI: 1.03–1.16) for lag 0–25.

Conclusions: Both high and low temperatures were associated with increased mortality amongst pre-weaned calves of 15–55 days, whereas associations in weaned calves (56 days – 1 year) were only observed for low temperatures and in newborn calves of at most 14 days and lactating cattle >2 years only for high temperatures. Associations of air pollution with mortality in all age groups were not consistent, except for the effect of ozone of lag 0–7 and lag 0–25.