Heat waves analysis and the heat load of agricultural workers during the heat waves in 2017 (using index WBGT) | Obravnava vročinskih valov in primer toplotne obremenitve delavcev v kmetijstvu v času vročinskih valov 2017

English. Workers in agriculture are regularly exposed to heat stress during summer, which can affect reduced labour productivity and income losses. Air temperatures in Slovenia have been rising in recent decades, and climate change projections show that this trend will continue along with an increase in the number of days with heat stress risk. Changes in the number of heat waves in central and south-western Slovenia for the period 1961–2017 were analysed as well as the risk of the heat stress for workers during heat waves in the year 2017. The heat wave occurs if the temperature threshold for the average daily temperature is reached or exceeded on at least three consecutive days, with the threshold for the mild continental climate (Ljubljana) 24 °C and the mild Submediterranean climate (Bilje) 25 °C. The WBGT (Wet Bulb Globe Temperature) index, assessing the risk of heat stress, was calculated from relative humidity and air temperatures. At both locations, the number of days in heat waves increased as well as their intensity, average daily air temperatures were significantly higher than in the first half of the considered period. The time span, in which the heat waves occur, also extended, as until 1990 they did not appear in early June and late August, as in recent years. The calculated values of the WBGT show that for most days in the heat waves in 2017 in Ljubljana and Bilje, the WBGT 23 °C threshold was exceeded practically all day, which shows a high level of heat stress risk for physically intense work. In the case of exceeded WBGT reference values, employers or farmers themselves should take actions to reduce the risk of heat stress.

Slovenian. Delavci v kmetijstvu so poleti v veliki meri izpostavljeni vročinskemu stresu, kar lahko vpliva na zmanjšano storilnost in izgubo dohodka. Temperature zraka v Sloveniji v zadnjih desetletjih naraščajo, projekcije podnebnih sprememb pa kažejo, da se bo ta trend nadaljeval hkrati s povečanjem števila dni z vročinskim stresom. Analizirali smo spremembe v številu vročinskih valov v osrednji in jugozahodni Sloveniji za obdobje 1961–2017 ter obremenitev delavcev z vročinskim stresom med vročinskimi valovi na primeru leta 2017. Vročinski val nastopi, če je temperaturni prag za povprečno dnevno temperaturo dosežen ali presežen vsaj tri zaporedne dni, pri čemer je prag za omiljeno celinsko podnebje (Ljubljana) 24 °C in za omiljeno sredozemsko podnebje (Bilje) 25 °C. Kazalnik za spremljanje toplotne obremenitve delavcev WBGT (Wet Bulb Globe Temperature) smo izračunali iz temperatur zraka in zračne vlage. Na obeh lokacijah se povečuje število dni v vročinskih valovih in njihova intenzivnost, povprečne dnevne temperature zraka dosegajo precej večje vrednosti kot v prvi polovici obravnavanega obdobja. Podaljšuje se tudi časovni razpon, v katerem se pojavljajo, saj se do leta 1990 vročinski valovi niso pojavljali zgodaj junija in pozno avgusta, tako kot v zadnjih letih. Izračunane vrednosti kazalnika WBGT kažejo, da je bila v večini dni v vročinskih valovih 2017 v Ljubljani in Biljah mejna vrednost WBGT 23 °C presežena praktično cel dan, kar za delavce z veliko fizično obremenitvijo pomeni visoko stopnjo tveganja zaradi obremenitve z vročinskim stresom. Pri preseženih mejnih vrednostih WBGT bi morali delodajalci oziroma kmetje sami uvesti preventivne ukrepe za zmanjšanje tveganja vročinskega stresa.