How long should a covering letter for a job be?

I need to cover the following points:
Responsibilities for this position include but are not limited to:
Development and production of new health promotion material including but not limited to: information booklets, posters, workshops, presentations and online health promotion material.
Assisting with health and injury prevention related research.
Using communication skills and behaviour change methodology to assist individuals to make positive health and lifestyle changes.
Effective and efficient management of assigned tasks.
Occasional delivery of health promotion related services.
Necessary qualifications and skills include:
Tertiary degree in Health Science or related tertiary discipline
Excellent research skills
Excellent creativity skills
Microsoft Office and PowerPoint skills
Exceptional presentation skills are essential
Manual Driver's licence & vehicle
Desirable qualifications and skills include:
Experience in graphic design, with Adobe InDesign skills preferred
Current Level 2 First Aid

A cover letter is always a good idea. It gives enough information about you and your capabilities so that the employer will be interested in talking with your personality.
The letter should relate specifically to the company and person to whom you are writing. If you haven't already done so, find out as much as you can about each firm and individual you plan to ask for an interview. Try to talk with some one who has been working with the firm, ask for literature, such as the annual report that explains the firm and its policies, check the company's WEB SITE, or check out the firm at Hoover's Online, The Wall Street Journal's Career Journal or Wet Feet's Company Profiles.
1. Use correct grammar.
2. Address it to a specific person by name, including the job title in the inside address.
Include the following:
a) Brief greeting including how you heard about the opening
b) The position you are applying for
c) Your basic qualifications for the position and any accomplishments or career highlights that might interest the employer enough to contact you
d) Any other information you feel is pertinent to the specific job without repeating information found in your resume. Justify any holes in the resume if necessary, like the five year gap when you didn't work at all!
e) End with a paragraph requesting an interview, including your phone number and e-mail address and when you can be reached.
BE SURE YOU INCLUDE THE DATE ...A RETURN ADDRESS... AND AN INSIDE ADDRESS.
E-mails don't need addresses.
Sign the letter in blue or black ink only. NO EMOTICONS :)

I will answer your question the way my former english teacher put it. She said it was like a woman's skirt, long enough to cover the subject, but short enough to keep it interesting. Most of the things listed should go in your resume, not your cover letter.

Those things should be covered in the resume not the cover letter. The cover letter should be a short one page. It should say where you heard of them and what made you think you qualified to apply. Then close with inviting them to contact you and your contract information.