Construction and materials stocks were the worst performing stocks on Wednesday with blue-chip constituent CRH among the heaviest fallers.After a strong performance in morning trade, UK stock markets swung into the red after the European Commission at noon cut its forecasts for gross domestic product growth in the Eurozone this year to 0.1%, from 1% before. The news dented sentiment in cyclical sectors such construction on concerns that weaker economic growth across the continent will result in reduced demand for services.CRH, the FTSE 100 building materials group, was trading 3.16% lower at 1,166p in the afternoon session after gaining over 8% in the past two weeks.Shares fell in sympathy with Switzerland-based cement maker Holcim which missed profit forecasts in the third quarter.AIM-listed construction stock Morgan Sindall was extending yesterday's losses following a profits warning and the resignation of its Chief Executive Paul Smith.The company said that underlying trading for the current year is now expected to be slightly below previous forecasts.Elsewhere in the sector, James Halstead, Marshalls, Heller, Galliford Try and Balfour Beatty were also trading firmly in negative territory. Top performing sectors so far todayHealth Care Equipment & Services 3,674.40 +0.60%Tobacco 36,236.37 +0.53%Electronic & Electrical Equipment 3,440.87 +0.43%Industrial Engineering 7,799.01 +0.36%Technology Hardware & Equipment 891.31 +0.28%Bottom performing sectors so far todayConstruction & Materials 3,374.16 -2.66%Personal Goods 19,324.03 -1.83%Fixed Line Telecommunications 2,654.94 -1.44%Industrial Metals & Mining 2,683.45 -1.36%Banks 4,187.27 -1.29%BC