What's the Difference between MND and ALS? Are the names interchangeable?

The term Motor Neurone Disease actually describes a group of very similar conditions that affect motor neurones. Amyotrophic lateral sclerosis (ALS) is the most common type of MND and affects both the upper motor neurones (those running from the brain to spinal cord) and the lower motor neurones (those running from the spinal cord out to the muscles). Other types include Progressive muscular atrophy (PMA), which affects mainly the lower motor neurones, and Primary lateral sclerosis (PLS), in which only the upper motor neurones are damaged. Although each of the types of MND affects people in slightly different ways, there can be a great deal of overlap.

The name ALS is often used in America to describe MND in general. The disease is sometimes referred to in America as Lou Gehrig's Disease after the famous New York Yankees baseball player who contracted the disease in the 1930s.
Are there any specific occupations that may increase the risk of developing MND?
Researchers have investigated a number of occupations where the employees may be at a slightly greater risk of developing MND. These include military service, particularly Gulf War Service ; electrical industry, agriculture and sports, particularly football. The factors that may increase the risk of developing MND in these occupations includes exposure to chemicals known as organophosphates, to electrical trauma and to high levels of physical exercise. The evidence ranges from anecdotal reports to publication of contradicting research papers. While all of these factors may contribute to the risk of developing MND, none of them cause the disease on their own.