Doctors and scientists who have worked here say serious health problems have resulted for many of the industry's 50,000 workers, more than 70 percent of them women. Researchers say their work is hampered by lack of access to flower farms because of reluctant growers. But studies that the International Labor Organization published in 1999 and the Catholic University issued here last year showed that women in the industry had more miscarriages than average and that more than 60 percent of all workers suffered headaches, nausea, blurred vision or fatigue.

''No one can speak with conclusive facts in hand about the impact of this industry on the health of the workers, because we have not been able to do the necessary studies,''said Dr. Bolívar Vera, a health specialist at the Health Environment and Development Foundation in Quito. ''So the companies have been able to wash their hands of the matter.''

In the 20 years since the farms started here, Ecuador has out of nowhere become the fourth-largest producer of roses in the world, with customers from Kazakhstan to Kansas.

St. Valentine's Day is the biggest rose event in the United States, which buys more than 70 percent of its cut flowers from South America and is Ecuador's biggest trading partner. Roses retail for up to $6 a bloom. Last week, workers at RosaPrima, a plantation here, moved at a dizzying pace to cut, wrap and box 70,000 stems a day. Computers help supervisors track each stem and each worker's productivity.

The general manager, Ross Johnson, said he was proud of his business and especially his workers. He said that a doctor visited the farm several times a week and that all workers wore gloves and protective equipment, whether or not handling chemicals. Mr. Johnson said he had cracked down on contractors who hired children as temporary workers.