SHIPBOARD SANITATION IS an important and vital part of cruising, but you won't find the subject covered in those glossy travel folders. The U.S. Public Health Service periodically inspects all ships that dock at U.S. ports. PHS inspections are rigid and strict, covering 32 items in six categories. The passing grade is 84.

Some vessels pass. Others do not. A cruise line gets 100 percent at one inspection and fails at the next. It's a never-ending process. The lines at PHS do work closely together, a partnership essential to passengers' welfare and safety.

In recent years, stories about outbreaks of gastrointestinal illness and diarrhea aboard some ships have made headlines, and the operators felt that some press and TV coverage was unfair. However, since those stories appeared, additional health precautions have been taken by cruise line officials, and the amount of shipboard illness had decreased.

In the wake of adverse publicity, the lines agreed with a PHS recommendation that sanitation officers be stationed aboard ships or at least work from time to time on each vessel, according to John H. Reurs, chairman of the New York committee of the International Committee of Passenger Lines. Reurs is spokesman for 15 member lines with more than 50 ships at sea.

We queried a number of cruise lines recently and found varying degrees of compliance. Here's what some of the lines are doing:

CARNIVAL CRUISE LINES, Miami. Robert H. Dickinson, vice president-sales: "We've hired a full-time sanitation expert who is training and supervising all crews in sanitation and health-related problems. This expert travels from ship to ship periodically.All crew members wear rubber gloves."

COMMODORE CRUISE LINE LTD., Miami. David Y. Levene, general sales manager. "We were recently inspected here [Miami] and in St. Thomas and got 100 percent. We have special crew members in charge of keeping up our good standards."

COSTA CRUISES, New York.David Stollmeyer, executive vice president: "In May the staff caption of each ship was given the responsibilities of twice-a-week health inspection aboard his vessel. We also have three technical engineers who check all systems to make certain refrigeration, chlorination of water and everything else is in top shape. We've also instituted a new hotel department whose director supervises proper food preparation, storage and handling. We do this for all ships in both Genoa and the U.S."

CUNARD LTD., New York. "We recently appointed a permanent hygiene officer aboard the QE2. He sees that the ship meets public health regulations and standards. He coordinates this between ship and shore. The staff captain aboard the Countess and Princess has put a person in charge of maintaining health standards. That person reports directly to him. The QE2 recently made 94 percent and the Countess, 100. The Princess is out of the country."

EASTERN STEAMSHIP LINES INC., Miami: Ellie Esser, vice president, public relations/advertising: "We have a sanitation officer on the Emerald Seas. We recently got 100 percent."

HELLENIC MEDITTERANEAN LINES, New York: Ralph Hartl, president (U.S.): "We've haven't done too well in the past, but we now have our chief steward in charge of maintaining sanitation standards. By the time the Aquarius sails in December to the Caribbean from San Juan, we hope to get better than a passing grade."

HOLLAND AMERICA CRUISES, New York: John H. Berry, president: "We have a resident sanitation officer who is always aboard each of our ships. He works closely with PHS. If new equipment needs to be installed, he handles it.

"We bagan staffing our fleet with sanitation officers on June 1, 1978. Each officer has a bachelor of science or master's degree in science in the field of public health or environmental sanitation from an accredited U.S. university. Each has considerable field experience.

"We are the only cruise line with resident professional sanitation officers. All of our vessels are equipped with the finest electronic monitoring devices to document the potability of the drinking water and thereby ensure our passengers' health and protection. Our swimming pools are filtered and disinfected.

"All galley equipment purchased, including refrigeration and dishwashers, are all National Sanitation Foundation approved. There is a shoreside technician who inspects and maintains the dish- and glass-washing equipment each time a ship returns to its port of origin. Our sanitation officers are continually training the food-handling staff on a one-to-one basis.

"We are now adding an extra of giving passengers an opportunity of requesting a nonsmoking section in the dining rooms of all five ships. Nonsmoking areas are also available in each ship's main lounge."

HOME LINES, New York. "The senior officers aboard both the Oceanic and Doric are responsible for upholding our high standards. We are consistently getting a 98 grade. Soon it will be 100."

ITALIAN LINE CRUISES INTERNATIONAL, New York. Luciano Galloni, general manager: "As you know from the recent press we received, we failed to pass PHS inspection because we chlorinate water by hand rather than automatically. We now have new equipment which is being installed as quickly as possible. We are also correcting our refrigeration and other items. I am strongly urging our Italian management to appoint qualified sanitation personnel for the Marconi and for a second ship, the Galileo, scheduled to begin sailing Oct. 20 from Florida. Incidentally, we are correcting items aboard this ship before it begins cruising. We want to cooperate fully with PHS. We are also planning a special sanitation training program for our crew, a bit of a problem; we change crews every four to six months."

(Note: Last month the Italian line suspended the Marconi's cruise service, cancelling the balance of her 1979 schedule to allow time for completion of modifications needed to meet PHS specifications.)

NORWEGIAN AMERICA LINE, New York: "We follow all procedures."

NORWEGIAN CARIBBEAN LINES, Miami. Wendy Marston, marketing: "The staff captain and chief steward of each ship conduct constant checks to see that everything is in order, following PHS recommendations. Our hotel manager works with the two men and inspects food and its preparation and storage. Inspections are part of our regular routine."

PAQUET FRENCH CRUISES, New York. William Schanz, president: "The staff captain is responsible for meeting the PHS criteria. He inspects and oversees the 32 points. This includes training of crew."

PRINCESS CRUISES, Los Angeles. Nancy Miller, special promotions manager: "We always have had a sanitation officer who sails aboard each ship. He has his own rating system and it is more strict than that of PHS. We have done well on PHS inspections and plan to continue so."

ROYAL CARIBBEAN CRUISE LINE, Miami. Bill Chambers, marketing service manager: "We do have a sanitation officer aboard ship. Each ship's crew works on this also."

ROYAL CRUISE LINE, San Francisco. Duncan Beardsley, senior vice president: "The staff captain aboard our Golden Odessey is responsible, working closely with the ship's doctor. In the past we didn't pass inspection, but we do now."

ROYAL VIKING LINE, San Francisco. Warren Titus, president: "The staff captain on each ship is the sanitation officer. We maintain a very strict code to meet PHS requirements, which we do. We feel that the health of our passengers and their safety are our prime obligations."

SITMAR CRUISES, Los Angeles. Steve Shanesy, public relations: "The captain of each ship is in charge of public health aboard each of our ships. Our Fairwind recent made 100 percent."