Adjusted EBITDA for our Polyurethanes division in the first quarter of 2013 was $178 million. We saw a meaningful earnings improvement in our MDI Urethanes business compared to the prior year. This was offset by lower PO/MTBE earnings, which benefited the first quarter of 2012 by approximately $60 million from industry supply outages.
In the first quarter of 2013, we successfully raised our MDI selling prices and we're able to offset the increase in raw material costs. The cost of our largest raw material, benzene, increased in the first quarter by approximately 20% compared to the prior year. We saw strong growth and demand for our MDI urethanes in the Asia Pacific and North American regions.
Our largest markets in the Asia Pacific region are insulation, adhesives, coatings and elastomers and automotive. We saw a double-digit growth in these markets primarily as a result of more demanding energy codes for building construction favoring MDI and strong Chinese automotive demand.
In the Americas, we're seeing signs of a continued recovery in housing and construction. Our largest market, composite wood products, grew at double-digit rates.
In the European region, we saw soft demand in Northern Europe for the first time since the European financial crisis. Some of this is seasonal due to the prolonged cold winter negatively impacting our largest market, construction, insulation. We also felt the impact of lower European automotive demand. We booked blend propylene oxide-based polyols with MDI to create specific polyurethanes system solutions for our customers.
In the U.S., we manufacture our own propylene oxide. MTBE is the byproduct of our manufacturing process. Lower-priced butane in 2013 partially offset the decrease in average selling prices that resulted from industry supply outages last year.
This past week, we were forced to declare force majeure in Europe on the supply of certain grades of pure and variant MDI products. The situation was caused by a lack of critical raw material supply and offtake from our MDI facility in Rotterdam, the Netherlands.
We estimate the EBITDA impact on the second quarter 2013 to be approximately $15 million. As of this morning, our operations appear to be in better shape than last week. Barring any supply chain disruption, we hope to return to normal operations in the next 2 to 3 weeks.