One possible version:
Dear Mike，
Thank you very much for your concern. Last months several places in Beijing were blanketed with thick yellow fog. Everything around disappeared from oursight. Some highways were closed. Traffic jams were commonly seen in the streets. Many people, especially children and seniors, even found it difficult to breathe. As a result, local hospitals were crowded with people who had problems with their noses and lungs. Part of the cause was the dry weather, but the severely damaged environment contributed a lot to this nightmare. Personally I didn't get any health problems in the haze because I stayed mostly indoors.But to make a significant change we really have to do more to protect our environment. To live a better life we have to push on with the economy, but it wound be meaningless if we have to achieve it at the cost of our breathing air.
Regards!
Yours，Li Hua
【參考譯文】
一個可能的版本：
親愛的邁克，
非常感謝你的關心。上個月在北京的幾個地方覆蓋了厚厚的黃色的霧。周圍的一切從我們的視線中消失了。一些高速公路被關閉。街道上經常看到交通堵塞。許多人，尤其是兒童和老人，甚至覺得呼吸困難。結果，當地醫院擠滿了鼻子和肺部有問題的人。部分原因是乾燥的天氣，但嚴重破壞環境作出了很大貢獻這個噩夢。就我個人而言，我在霧霾中沒有任何健康問題，因為我大部分都呆在室內，但要做出重大的改變，我們必須做更多的事情來保護我們的環境。為了過上更好的生活，我們必須繼續推動經濟發展，但如果我們必須以呼吸的空氣來達到目的，那就毫無意義了。
當做!
你的，Li Hua