Radiation levels in Hawaii from Japan’s nuclear crisis continue to fall, government monitoring shows.

Milk tested at a dairy in Hilo on April 4 registered 24 picocuries per liter for cesium-134, 19 picocuries for cesium-137 and 18 picocuries for iodine-131, according to the U.S. Environmental Protection Agency.

Milk samples tested again on April 13 — the most recent data — showed 11 picocuries for cesium-134, 11 picocuries for cesium-137 and a “non-detect” level for iodine-131.

At either level the radiation posed no public health risk, state officials have said.

“We considered it safe before, and I can’t even say it’s safer now, because we were safe to begin with,” said Jeff Eckerd, acting program manager of the state Health Department’s indoor and radiological health branch. “The numbers are coming down, so we’re good.”

Air monitoring on Kauai April 1-3 and on Oahu April 1-4 recorded non-detect levels for all isotopes tested. Honolulu rainwater was found to have 2.2 picocuries per liter for iodine-131 on April 7.

The EPA has been conducting water and milk testing, “and they are a little delayed” with other results, Eckerd said yesterday. “I’m trying to get updated air monitoring readings from them.”

The U.S. Food and Drug Administration’s “derived intervention level” — the point at which steps would be taken to safeguard the public — is 33,000 picocuries for the combined cesium isotopes and 4,700 picocuries for iodine-131. At those levels the sale of affected milk could be stopped.

A separate standard is the EPA’s “maximum contaminant level” for radiation in water at 3 picocuries per liter. But that presumes a 70-year consumption of two liters a day with that level of radiation.

Results might be available today or tomorrow from Health Department testing done April 18 and 19 at large-scale rainwater catchment systems on Hawaii island, Maui and Kauai, Eckerd said.

Eckerd said he would be “really surprised” if the levels are above the recent 2.2 picocuries-per-liter rainwater detection.

Based on numbers seen so far, private rainwater catchment radiation levels “wouldn’t be harmful,” Eckerd said.