TABLE 2-1 Dose-Response Relationships at Relatively Low Doses

System (including exposure conditions and acute αa or LDRb)

End Point

Dose Range, mGy

Curve Shape

Frequency of Events per Viable Cell per Milligray

Comments and References

Human fibroblasts in G0

Immediate PCC fragments

109–6000 (acute)

Linear

6 × 10−3

LNTc extrapolates to 5 mGy (Cornforth and Bedford 1983)

Human fibroblasts in G0 α-component-metaphase

Chromosome dicentrics and rings

1000–12,000 (acute)

Upward curvature

5.8 × 10−5

(Cornforth and Bedford 1987)

Immortal human lymphocytes in G2

Chromatid gaps

50–500 (acute)

Linear

2.5 × 10−5

LNT > ~50 mGy (Puck and others 1997)

Human lymphocytes in G0 (six laboratories)

Chromosome dicentrics

3–300 (acute)

Linear

2.9 × 10−5

LNT > ~20 mGy (Lloyd and others 1992)

Human primary fibroblasts in G0 (acute α-component)

Chromosome aberrations

1000–6000 (acute)

Upward curvature

5.8 × 10−5

α-Component for acute corresponds to linear dose-response for LDR (Cornforth and others 2002)

Human primary fibroblasts in G0-0.5 or 1 mGy/min

Chromosome aberrations

300–6000 (LDR)

Linear

4.9 × 10−5

LNT > 300 mGy (Cornforth and others 2002)

Mice—daily doses of 6.4, 18.5, or 55 mGy for 21, 42, or 63 d, respectively

Chromosome translocations

100–3500 (LDR)

Linear

1.2 × 10−5

LNT > ~100 mGy DDREFd of 4–6 for 1–2 Gy acute exposure (Tucker and others 1998)

Nuclear workers at Sellafield—lymphocyte cultures

Chromosome translocations

50–1000 (LDR)

Linear

1.1 × 10−5

LNT > 50 mGy (Tawn and others 2000a, 2004)

Cleanup workers at Chernobyl—lymphocyte cultures

Chromosome translocations

~95 (LDR)

?

1.9 × 10−5

Increase of 30% (10–53% p < .002) relative to controls (Jones and others 2002)

Chinese hamster cells with human chromosome 11

Loss of antigen on chromosome 11

250–1500 (acute)

Linear

7 × 10−6

LNT > ~ 250 mGy (Puck and Waldren 1987)

TK6 human lymphoblasts—daily doses of 10, 25, 50, or 100 mGy for 1 month

HPRT mutations

50–2000 (LDR)

Linear

6 × 10−9

LNT > ~50 mGy (Grosovsky and Little 1985)

Mice—T lymphocytes in spleen—chronic at 0.69 mGy/min or 0.1 mGy/min

HPRT mutations

300–6000 (LDR)

Linear

3 × 10−9

LNT > ~300 mGy DDREF of ~1.5 for acute <2 Gy (Lorenz and others 1994)

Cleanup workers at Chernobyl—lymphocyte cultures

HPRT mutations

~95 (LDR)

?

5 × 10−8

Increase of 41% (19–66% p < .001) relative to controls (Jones and others 2002)

Chinese hamster cells with human chromosome 11

Genomic instability Translocations on chromosome 11

1000–10,000 (acute)

Linear

3 × 10−5

Based on percent unstable clones with BrdU saturates at 30% (Limoli and others 1999)

Chinese hamster cells (CHO)

Genomic instability de novo HPRT mutations

2000

?

5 × 10−5

Based on percent unstable clones; from 4 to 12 Gy saturates at 20% (Little 1998)

Melanocytes in irradiated mice

Genomic instability gene deletions

10–1000

Linear

8 × 10−5

LNT > 10 mGy, but supralinear from 0 to 10 mGy (Schiestl and others 1994)



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