Neither BP nor Deepwater Horizon Unified Command appear to be systematically tracking worker illnesses in a way that notes possible causes, such as exposure to petroleum fumes or dispersant.

"They don't have any documented reports of people getting sick from chemical exposure, and that's why there's not a breakdown," Ayla Kelley of the Coast Guard told me, after she asked around at Unified Command's Joint Information Center.

But the log of illness and injury kept by Unified Command and released by BP late last week indicates there have been sicknesses that may be related to chemical exposure.

Records of specific incidents describe mostly physical injuries -- cuts, back or neck pain, sprained ankles, possible insect bites, and injuries from lightning. Only seven records describe problems that could even be construed as illnesses:

• "Heat-related illness, motion sickness" (May 6)
• "IP was checking spray nozzles on airplane, sprayed in face with dispersant when he took a nozzle off the boom under pressure" (May 7)
• "person collapsed at the safety training" (May 10)
• "Worker noticed rash on both arms and neck after completing beach cleanup" (May 25)
• "Suspected inhalation of crude oil vapors" (June 7)
• "Worker dizzy, nauseated, chest tightness, ache in left shoulder" (June 8)
• "Chest pains" (June 9)

Dispersants are mentioned. Crude oil vapors are mentioned. And yet aside from these few mentions, there's no information that tracks broadly what sick workers have been exposed to, or what may be causing these sicknesses -- be it heat, dispersant, fumes from the oil, or any number of causes that other state agencies are tracking and making public.

Experts we've spoken with have pointed out that epidemiology is imprecise, and that determining causation in potential chemical exposure cases is a challenge. But it's one thing to say, "We're not sure, but here's what the workers were exposed to," and it's another thing to not track it at all.

There may be a reason, however, that the BP and Unified Command records provide such limited data.

I spoke with Franklin Mirer, a toxicologist and professor at Hunter College of the City University of New York, who told me that because BP and Unified Command use OSHA guidelines to judge whether an incident is recordable, "they would miss almost everything" related to chemical exposure.

"It's not complete," Mirer said. He also said that OSHA has been trying to modernize these injury and illness recording guidelines.

When I asked BP spokesman Mark Proegler whether logs were being kept of health complaints believed to be related to chemical exposure, he did not answer directly.

"We take these complaints seriously, investigate them, and take corrective action as necessary," Proegler said. He added that there is a Deepwater Horizon Medical Support line that individuals may call to report health issues, and calls to that line are being tracked.