There are studies that show that grilling can present a health risk because carcinogenic compounds can form when meat is cooked at high temperatures over direct heat sources. 

Cooking over high flames turns chemicals found naturally in muscle meats and fish into cancer-causing substances known as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs). Both have been linked to an increased risk of several cancers, including colorectal cancer, breast cancer and prostate cancer.  High-temperature cooking — over 300 degrees Fahrenheit — and the length of time a food is heated trigger their formation.

PAHs get into food when dripping meat juices cause the grilling surface or coals to flare up, engulfing the meat or fish in fragrant, but toxic, vapors. You can also reduce the risk by:

• Removing visible fat that can cause a flare-up. Flare-ups burn foods and this increase HCA formation.
• Using foil. You can also reduce flare-ups by spreading aluminum foil on the grill. Make small holes in the foil to allow fat from the meat to drain.
• Precooking meat in the microwave immediately before placing it on the grill to release some of the juices that can drop on coals. Microwaving meats for a couple of minutes before placing them on the grill can cut the effects of HCAs about 90 percent. The microwave draws liquid out of the meat, which in turn reduces flare-ups on the grill.
• Turning down the heat. HCA forms when proteins in meats (including pork, poultry and fish) are exposed to high heat.  When fats and juices drip onto the hot fire, flare-ups can deposit the chemical onto meat surfaces. You can easily avoid the risk by reducing the heat. Grill meat on glowing embers instead of high flames or lower gas heat from high to medium. On a gas grill, move the rack up a notch to distance foods from the flames.
• Using smaller cuts of meat. Smaller cuts spend less time over the flame than big slabs of meat. The longer you grill your meat, the more the carcinogens develop. Less time over the flame means less HCAs.
• Flipping the meat frequently. Turning meat over every minute greatly reduces HCAs.
• Using tongs to turn foods. Puncturing meats with a fork may cause juices to flow and drip on to the coals.
• Avoiding over cooking. The longer you grill your meat, the more the carcinogens develop. The charred bits on foods are the largest sources of PAHs and HCAs so if you have charred sections of meat cut them off.
• Cooking food in the center of the grill and moving coals to the side to prevent fat and juices from dripping on them.
• Adding anti-cancer soy to the mix. Mix 1/2-cup of textured soy protein into a pound of ground meat before grilling. This cuts 95-percent of the expected HCAs in burgers without affecting taste.
• Giving the meal a Vitamin E boost. 20 milligrams of vitamin E powder mixed into or sprinkled on 3.5-ounce patties can reduce HCA formation as much as 72-percent. You can use a capsule of vitamin and crack it open for contents.
• Marinating with herbal antioxidants.  Recently scientists at the Food Safety Consortium project at Kansas State University have discovered that herbs of the Lamiaceae family (Basil, Mint, Rosemary, Thyme, Oregano, and Sage) used in marinades reduced HCA formation dramatically. A citrus or olive oil marinade can also counteract HCA buildup.
• Use marinades based on olive oils and/or citrus juices. Use herbs like Basil, Mint, Rosemary, Garlic, Thyme, Oregano, and Sage to add flavor and reduce HCA formation in foods. These herbal antioxidants reduce the formation of free radicals (bad stuff) when meat hits heat. A citrus or olive oil marinade can also counteract HCA buildup.
• Such marinades may reduce HCA formation in meat and fish by up to 99 percent.
• Cutting charred portions off the meat before eating.

If you follow these rules not only will you greatly reduce the risk of these cancer agents but you will reduce the fat in meats that you grill.