tailieunhanh - The principles of toxicology environmental and industrial applications 2nd edition phần 10

Methysergide, một chất đối kháng serotonin, có lẽ là thành phần chủ yếu gây ảo giác của ergot. Một số khuôn mẫu đã được tìm thấy để sản xuất chất gây ung thư được gọi là aflatoxin và ochratoxins, thích hợp lưu trữ các loại cây trồng | 546 CONTROLLING OCCUPATIONAL AND ENVIRONMENTAL HEALTH HAZARDS deliver scavenging nosepiece. The nosepiece should seal against the face of the wearer to minimize loss from around the face to facepiece seal. A prototype local exhaust ventilation system was developed for use in the dental operatory. With proper positioning it was found to reduce exposure levels to nitrous oxide to below 25 ppm procedure TWA . Further studies indicated that positioning of the ventilation system is critical. The total volumetric flow rate must be kept to less than about 600 cfm cubic feet per meter to prevent backflow down chimneys in home-type offices while the capture velocity must be kept above 80 fpm at the mouth to efficiently capture nitrous oxide emitted from the mouth. Fiberglass Layup Operation Many of the boats golf carts and even some of . cars are made from fiberglass which reinforces a polystyrene outer coating. The process involves spraying a polyester resin in a styrene monomer solvent called the gel coat onto a mold. The spray gun mixes the resin solvent at the tip with MEK peroxide a catalyst used to hasten the polymerizing reaction. The gel coat is allowed to dry and then fiberglass is applied along with a mixture of polyester resin and styrene monomer MEK peroxide and acetone to liquify the surface and allow the fiberglass mixture to adhere to the gel coat through a chopper gun which is much like a spray-paint gun except that it has an additional blade which rotates around the opening to cut the long fiberglass strands. After the fiberglass mixture dries the product is separated from the mold and surfaces are smoothed by sanding. Some pieces require actual cutting and grinding to provide the proper fit. In one such operation the gel coat sprayer was located in a separate room with an exhaust fan located in the wall. The sprayer wore a full-body covering synthetic rubber gloves and an air-supplied hood while spraying gel coat. His 8-h TWA exposure to styrene vapor .