By contrast, smoking cannot be beneficial for people’s health, and even this cause damage for the health of smokers as well as people around them.

我认为，这个句子错误不少。表现在：

1. By contrast（相比之下），应为 On the contrary（与此相反）

2. be beneficial for sth. 改为  be beneficial to sth. 

3. cannot be 表推测，这是不需要推测的，已经是事实。不如直接用否定 is not beneficial to。

4. this cause  改为： it causes

5. it causes damage for 改为：it causes damage to

本句，用 and 连接没有问题。句子结构的否定肯定，要服从于语义：两个分句都讲吸烟的害处，用 and 没有问题。

       ... damage for 应该改为： ... damage to

       and 连接两个句子时，可以是一个为肯定句另一个是否定句。如：Her English is good and her Japanese is not bad. 她英语好，日语也不差。（摘自《牛津英语用法指南》第四版 226.1）

       这里用this来指代smoking是可以的。

1. cannot be - 不要这么写哦，英语口语才有这样的表达。

2. By contrast, smoking is not beneficial for people’s health, and even causes

   damage to the health of smokers as well as people around them.

3. 考虑不要用this, 最好用 it even causes......

4. and 在这里可以用，注意你的句子中

   By contrast, smoking cannot be beneficial for people’s health, and even this

   cause damage for the health of smokers as well as people around them.

   前面是否定，后面是肯定。