With the massive oil spill in the Gulf of Mexico now in its sixth week, reports of clean-up workers falling unwell are on the rise.

Within the past week, they have seen a number of workers hospitalized. Dr. Gina Solomon, a senior scientist with the Natural Resources Defense Council mentioned  that is new.

More than a dozen workers have been treated at local medical centers for flu-like symptoms ranging from chest pain to dizziness, nausea and headaches, presumably due to contact to diverse chemicals emanating from the slick, according to news reports.

The Unified Command in Louisiana — an alliance of administration agencies that includes the U.S. Coast Guard, the Department of the Interior and the National Parks Service — previous week called back to shore 125 boats helping with the clean-up after medical complaints from crew members.

Dispersants are chemicals used for the oil clean-up. The solvent used after the massive 1989 Exxon Valdez oil spill off the Alaska coast, for instance, was limonene, which can cause skin inflammation and asthma, said Robert Emery, vice president for safety, health, environment and danger organization at the University of Texas Health Science Center at Houston.

There’s no hesitation that people are getting sick out there in the Gulf of Mexico, Emery said. The key inquiry is what is it that is causing them to get sick.

BP and the U.S. Coast Guard have supposed dehydration, heat, food poisoning or other unrelated factors may have caused the workers’ symptoms. The Louisiana Department of Health and Hospitals is investigating, the Associated Press reported.

The U.S. Environmental Protection Agency reports that air superiority levels for ozone and particulates are standard on the Gulf coastline for this time of year. But, the organization added, it has detected some odor-causing pollutants associated with petroleum products along the coastline at low levels. These chemicals could be  a reason of headache, nausea and throat irritation.

BP CEO Tony Hayward has mentioned that the symptoms that workers are reporting — dizziness, headaches, coughing — could be due to any quantity of causes, as well as diesel fumes, exhaustion and heat from wearing Tyvek defense suits.